BACKGROUND

Angiotensin-converting enzyme 2 (ACE2) is a pleiotropic monocarboxypeptidase capable of metabolizing several peptide substrates. We hypothesized that ACE2 is a negative regulator of angiotensin II (Ang II)-mediated signaling and its adverse effects on the cardiovascular system.

RESULTS

Ang II infusion (1.5 mg x kg(-1) x d(-1)) for 14 days resulted in worsening cardiac fibrosis and pathological hypertrophy in ACE2 knockout (Ace2(-/y)) mice compared with wild-type (WT) mice. Daily treatment of Ang II-infused wild-type mice with recombinant human ACE2 (rhACE2; 2 mg x kg(-1) x d(-1) IP) blunted the hypertrophic response and expression of hypertrophy markers and reduced Ang II-induced superoxide production. Ang II-mediated myocardial fibrosis and expression of procollagen type I alpha 1, procollagen type III alpha 1, transforming growth factor-beta1, and fibronectin were also suppressed by rhACE2. Ang II-induced diastolic dysfunction was inhibited by rhACE2 in association with reduced plasma and myocardial Ang II and increased plasma Ang 1-7 levels. rhACE2 treatment inhibited Ang II-mediated activation of protein kinase C-alpha and protein kinase C-beta1 protein levels and phosphorylation of the extracellular signal-regulated 1/2, Janus kinase 2, and signal transducer and activator of transcription 3 signaling pathways in wild-type mice. A subpressor dose of Ang II (0.15 mg . kg(-1) . d(-1)) resulted in a milder phenotype that was strikingly attenuated by rhACE2 (2 mg x kg(-1) x d(-1) IP). In adult ventricular cardiomyocytes and cardiofibroblasts, Ang II-mediated superoxide generation, collagen production, and extracellular signal-regulated 1/2 signaling were inhibited by rhACE2 in an Ang 1-7-dependent manner. Importantly, rhACE2 partially prevented the development of dilated cardiomyopathy in pressure-overloaded wild-type mice.

CONCLUSIONS

Elevated Ang II induced hypertension, myocardial hypertrophy, fibrosis, and diastolic dysfunction, which were exacerbated by ACE2 deficiency, whereas rhACE2 attenuated Ang II- and pressure-overload-induced adverse myocardial remodeling. Hence, ACE2 is an important negative regulator of Ang II-induced heart disease and suppresses adverse myocardial remodeling.

The interleukin 17 (IL-17) family, a subset of cytokines consisting of IL-17A-F, plays crucial roles in host defense against microbial organisms and in the development of inflammatory diseases. Although IL-17A is the signature cytokine produced by T helper 17 (Th17) cells, IL-17A and other IL-17 family cytokines have multiple sources ranging from immune cells to non-immune cells. The IL-17 family signals via their correspondent receptors and activates downstream pathways that include NFκB, MAPKs and C/EBPs to induce the expression of anti-microbial peptides, cytokines and chemokines. The proximal adaptor Act1 is a common mediator during the signaling of all IL-17 cytokines so far and is thus involved in IL-17 mediated host defense and IL-17-driven autoimmune conditions. This review will give an overview and recent updates on the IL-17 family, the activation and regulation of IL-17 signaling as well as diseases associated with this cytokine family.

Senescence is a highly organized and well-regulated process. As much as 75% of total cellular nitrogen may be located in mesophyll chloroplasts of C(3)-plants. Proteolysis of chloroplast proteins begins in an early phase of senescence and the liberated amino acids can be exported to growing parts of the plant (e.g. maturing fruits). Rubisco and other stromal enzymes can be degraded in isolated chloroplasts, implying the involvement of plastidial peptide hydrolases. Whether or not ATP is required and if stromal proteins are modified (e.g. by reactive oxygen species) prior to their degradation are questions still under debate. Several proteins, in particular cysteine proteases, have been demonstrated to be specifically expressed during senescence. Their contribution to the general degradation of chloroplast proteins is unclear. The accumulation in intact cells of peptide fragments and inhibitor studies suggest that multiple degradation pathways may exist for stromal proteins and that vacuolar endopeptidases might also be involved under certain conditions. The breakdown of chlorophyll-binding proteins associated with the thylakoid membrane is less well investigated. The degradation of these proteins requires the simultaneous catabolism of chlorophylls. The breakdown of chlorophylls has been elucidated during the last decade. Interestingly, nitrogen present in chlorophyll is not exported from senescencing leaves, but remains within the cells in the form of linear tetrapyrrolic catabolites that accumulate in the vacuole. The degradation pathways for chlorophylls and chloroplast proteins are partially interconnected.

Group I metabotropic glutamate receptors (mGluRs) induce a form of long-term synaptic depression (mGluR-LTD) in area CA1 of the hippocampus that requires rapid protein synthesis. Although much is known about the mechanisms underlying mGluR-LTD, it is unclear how mGluRs couple to the effectors necessary for translation initiation. A clue comes from work in the mouse model of Fragile X syndrome [Fmr1 knock-out (KO) mice], where group 1 mGluR stimulation of protein synthesis is absent and mGluRs are less associated with the postsynaptic scaffolding protein Homer (Giuffrida et al., 2005). Here, we examined the role of Homer interactions in mGluR-LTD and mGluR signaling to protein synthesis machinery in wild-type and Fmr1 KO animals. A peptide that mimics the C-terminal tail of mGluR5 (mGluR5ct), shown previously to disrupt Homer interactions with mGluRs, blocks mGluR-LTD and mGluR-signaling to protein synthesis initiation in wild-type animals. Disruption of mGluR-Homer interactions selectively blocks mGluR activation of the phosphoinositide 3-kinase (PI3K)-Akt-mammalian target of rapamycin (mTOR), but not ERK (extracellular signal-regulated kinase), pathway and translation of a 5' terminal oligopyrimidine tract containing mRNA, Elongation factor 1alpha. In Fmr1 KO mice, mGluR-LTD is insensitive to disruption of Homer interactions and mGluR activation of PI3K-mTOR is lost. Our results find specific roles for Homer in mGluR signaling and plasticity and suggest that reduced mGluR-Homer interactions in Fmr1 KO mice lead to a deficit in mGluR stimulation of translation initiation.

OBJECTIVE

Traditional blood glucose-lowering agents do not sustain adequate glycemic control in most type 2 diabetic patients. Preclinical studies with exenatide have suggested sustained improvements in beta-cell function. We investigated the effects of 52 weeks of treatment with exenatide or insulin glargine followed by an off-drug period on hyperglycemic clamp-derived measures of beta-cell function, glycemic control, and body weight.

METHODS

Sixty-nine metformin-treated patients with type 2 diabetes were randomly assigned to exenatide (n = 36) or insulin glargine (n = 33). beta-Cell function was measured during an arginine-stimulated hyperglycemic clamp at week 0, at week 52, and after a 4-week off-drug period. Additional end points included effects on glycemic control, body weight, and safety.

RESULTS

Treatment-induced change in combined glucose- and arginine-stimulated C-peptide secretion was 2.46-fold (95% CI 2.09-2.90, P < 0.0001) greater after a 52-week exenatide treatment compared with insulin glargine treatment. Both exenatide and insulin glargine reduced A1C similarly: -0.8 +/- 0.1 and -0.7 +/- 0.2%, respectively (P = 0.55). Exenatide reduced body weight compared with insulin glargine (difference -4.6 kg, P < 0.0001). beta-Cell function measures returned to pretreatment values in both groups after a 4-week off-drug period. A1C and body weight rose to pretreatment values 12 weeks after discontinuation of either exenatide or insulin glargine therapy.

CONCLUSIONS

Exenatide significantly improves beta-cell function during 1 year of treatment compared with titrated insulin glargine. After cessation of both exenatide and insulin glargine therapy, beta-cell function and glycemic control returned to pretreatment values, suggesting that ongoing treatment is necessary to maintain the beneficial effects of either therapy.

Little is known about the defensive mechanisms induced in epithelial cells by pathogenic versus probiotic bacteria. The aim of our study was to compare probiotic bacterial strains such as Escherichia coli Nissle 1917 with nonprobiotic, pathogenic and nonpathogenic bacteria with respect to innate defense mechanisms in the intestinal mucosal cell. Here we report that E. coli strain Nissle 1917 and a variety of other probiotic bacteria, including lactobacilli--in contrast to more than 40 different E. coli strains tested--strongly induce the expression of the antimicrobial peptide human beta-defensin-2 (hBD-2) in Caco-2 intestinal epithelial cells in a time- and dose-dependent manner. Induction of hBD-2 through E. coli Nissle 1917 was further confirmed by activation of the hBD-2 promoter and detection of the hBD-2 peptide in the culture supernatants of E. coli Nissle 1917-treated Caco-2 cells. Luciferase gene reporter analyses and site-directed mutagenesis experiments demonstrated that functional binding sites for NF-kappaB and AP-1 in the hBD-2 promoter are required for induction of hBD-2 through E. coli Nissle 1917. Treatment with the NF-kappaB inhibitor Helenalin, as well as with SP600125, a selective inhibitor of c-Jun N-terminal kinase, blocked hBD-2 induction by E. coli Nissle 1917 in Caco-2 cells. SB 202190, a specific p38 mitogen-activated protein kinase inhibitor, and PD 98059, a selective inhibitor of extracellular signal-regulated kinase 1/2, were ineffective. This report demonstrates that probiotic bacteria may stimulate the intestinal innate defense through the upregulation of inducible antimicrobial peptides such as hBD-2. The induction of hBD-2 may contribute to an enhanced mucosal barrier to the luminal bacteria.

The three-dimensional solution structure of the 40 residue amyloid beta-peptide, Abeta(1-40), has been determined using NMR spectroscopy at pH 5.1, in aqueous sodium dodecyl sulfate (SDS) micelles. In this environment, which simulates to some extent a water-membrane medium, the peptide is unstructured between residues 1 and 14 which are mainly polar and likely solvated by water. However, the rest of the protein adopts an alpha-helical conformation between residues 15 and 36 with a kink or hinge at 25-27. This largely hydrophobic region is likely solvated by SDS. Based on the derived structures, evidence is provided in support of a possible new location for the transmembrane domain of Abeta within the amyloid precursor protein (APP). Studies between pH 4.2 and 7.9 reveal a pH-dependent helix-coil conformational switch. At the lower pH values, where the carboxylate residues are protonated, the helix is uncharged, intact, and lipid-soluble. As the pH increases above 6. 0, part of the helical region (15-24) becomes less structured, particularly near residues E22 and D23 where deprotonation appears to facilitate unwinding of the helix. This pH-dependent unfolding to a random coil conformation precedes any tendency of this peptide to aggregate to a beta-sheet as the pH increases. The structural biology described herein for Abeta(1-40) suggests that (i) the C-terminal two-thirds of the peptide is an alpha-helix in membrane-like environments, (ii) deprotonation of two acidic amino acids in the helix promotes a helix-coil conformational transition that precedes aggregation, (iii) a mobile hinge exists in the helical region of Abeta(1-40) and this may be relevant to its membrane-inserting properties and conformational rearrangements, and (iv) the location of the transmembrane domain of amyloid precursor proteins may be different from that accepted in the literature. These results may provide new insight to the structural properties of amyloid beta-peptides of relevance to Alzheimer's disease.

Integral beta-barrel proteins are found in the outer membranes of Gram-negative bacteria, mitochondria, and chloroplasts. The assembly of these proteins requires a proteinaceous apparatus of which Omp85 is an evolutionary conserved central component. To study its molecular mechanism, we have produced Omp85 from Escherichia coli in inclusion bodies and refolded it in vitro. The interaction of Omp85 with its substrate proteins was studied in lipid-bilayer experiments, where it formed channels. The properties of these channels were affected upon addition of unfolded outer-membrane proteins (OMPs) or synthetic peptides corresponding to their C-terminal signature sequences. The interaction exhibited species specificity, explaining the inefficient assembly of OMPs from Neisseria in E. coli. Accordingly, the in vivo assembly of the neisserial porin PorA into the E. coli outer membrane was accomplished after adapting its signature sequence. These results demonstrate that the Omp85 assembly machinery recognizes OMPs by virtue of their C-terminal signature sequence.

Granulosa cells of mammalian Graafian follicles maintain oocytes in meiotic arrest, which prevents their precocious maturation. We show that mouse mural granulosa cells, which line the follicle wall, express natriuretic peptide precursor type C (Nppc) messenger RNA (mRNA), whereas cumulus cells surrounding oocytes express mRNA of the NPPC receptor NPR2, a guanylyl cyclase. NPPC increased cGMP levels in cumulus cells and oocytes and inhibited meiotic resumption in vitro. Meiotic arrest was not sustained in most Graafian follicles of Nppc or Npr2 mutant mice, and meiosis resumed precociously. Oocyte-derived paracrine factors promoted cumulus cell expression of Npr2 mRNA. Therefore, the granulosa cell ligand NPPC and its receptor NPR2 in cumulus cells prevent precocious meiotic maturation, which is critical for maturation and ovulation synchrony and for normal female fertility.

The amyloid beta-protein precursor gives rise to the amyloid beta-protein, the principal constituent of senile plaques and a cytotoxic fragment involved in the pathogenesis of Alzheimer disease. Here we show that amyloid beta-protein precursor was proteolytically cleaved by caspases in the <em>C</em> terminus to generate a second unrelated <em>peptide</em>, called <em>C</em>31. The resultant <em>C</em>31 <em>peptide</em> was a potent inducer of apoptosis. Both caspase-cleaved amyloid beta-protein precursor and activated caspase-9 were present in brains of Alzheimer disease patients but not in control brains. These findings indicate the possibility that caspase cleavage of amyloid beta-protein precursor with the generation of <em>C</em>31 may be involved in the neuronal death associated with Alzheimer disease.

OBJECTIVE

The aim of this study was to examine the relation of galectin-3 (Gal-3), a marker of cardiac fibrosis, with incident heart failure (HF) in the community.

BACKGROUND

Gal-3 is an emerging prognostic biomarker in HF, and experimental studies suggest that Gal-3 is an important mediator of cardiac fibrosis. Whether elevated Gal-3 concentrations precede the development of HF is unknown.

METHODS

Gal-3 concentrations were measured in 3,353 participants in the Framingham Offspring Cohort (mean age 59 years; 53% women). The relation of Gal-3 to incident HF was assessed using proportional hazards regression.

RESULTS

Gal-3 was associated with increased left ventricular mass in age-adjusted and sex-adjusted analyses (p = 0.001); this association was attenuated in multivariate analyses (p = 0.06). A total of 166 participants developed incident HF and 468 died during a mean follow-up period of 11.2 years. Gal-3 was associated with risk for incident HF (hazard ratio [HR]: 1.28 per 1 SD increase in log Gal-3; 95% confidence interval [CI]: 1.14 to 1.43; p < 0.0001) and remained significant after adjustment for clinical variables and B-type natriuretic peptide (HR: 1.23; 95% CI: 1.04 to 1.47; p = 0.02). Gal-3 was also associated with risk for all-cause mortality (multivariable-adjusted HR: 1.15; 95% CI: 1.04 to 1.28; p = 0.01). The addition of Gal-3 to clinical factors resulted in negligible changes to the C-statistic and minor improvements in net reclassification improvement.

CONCLUSIONS

Higher concentration of Gal-3, a marker of cardiac fibrosis, is associated with increased risk for incident HF and mortality. Future studies evaluating the role of Gal-3 in cardiac remodeling may provide further insights into the role of Gal-3 in the pathophysiology of HF.

'In dopaminergic neurons, alpha-synuclein (alphaS) partitions between a disordered cytosolic state and a lipid-bound state. Binding of alphaS to membrane phospholipids is implicated in its functional role in synaptic regulation, but also impacts fibril formation associated with Parkinson's disease. We describe here a solution NMR study in which alphaS is added to small unilamellar vesicles of a composition mimicking synaptic vesicles; the results provide evidence for multiple distinct phospholipid-binding modes of alphaS. Exchange between the free state and the lipid-bound alphaS state, and between different bound states is slow on the NMR timescale, being in the range of 1-10 s(-1). Partitioning of the binding modes is dependent on lipid/alphaS stoichiometry, and tight binding with slow-exchange kinetics is observed at stoichiometries as low as 2:1. In all lipid-bound states, a segment of residues starting at the N-terminus of alphaS adopts an alpha-helical conformation, while succeeding residues retain the characteristics of a random coil. The 40 C-terminal residues remain dynamically disordered, even at high-lipid concentrations, but can also bind to lipids to an extent that appears to be determined by the fraction of cis X-Pro peptide bonds in this region. While lipid-bound alphaS exhibits dynamic properties that preclude its direct observation by NMR, its exchange with the NMR-visible free form allows for its indirect characterization. Rapid amide-amide nuclear Overhauser enhancement buildup points to a large alpha-helical conformation, and a distinct increase in fluorescence anisotropy attributed to Tyr39 indicates an ordered environment for this "dark state." Titration of alphaS with increasing amounts of lipids suggests that the binding mode under high-lipid conditions remains qualitatively similar to that in the low-lipid case. The NMR data appear incompatible with the commonly assumed model where alphaS lies in an alpha-helical conformation on the membrane surface and instead suggest that considerable remodeling of the vesicles is induced by alphaS.

Hepatitis C virus (HCV) has a high propensity for persistence. To better define the immunologic determinants of HCV clearance and persistence, we examined the circulating HCV-specific T-cell frequency, repertoire, and cytokine phenotype ex vivo in 24 HCV seropositive subjects (12 chronic, 12 recovered), using 361 overlapping peptides in 36 antigenic pools that span the entire HCV core, NS3-NS5. Consistent with T-cell-mediated control of HCV, the overall HCV-specific type-1 T-cell response was significantly greater in average frequency (0.24% vs. 0.04% circulating lymphocytes, P =.001) and scope (14/36 vs. 4/36 pools, P =.002) among the recovered than the chronic subjects, and the T-cell response correlated inversely with HCV titer among the chronic subjects (R = -0.51, P =.049). Although highly antigenic regions were identified throughout the HCV genome, there was no apparent difference in the overall HCV-specific T-cell repertoire or type-1/type-2 cytokine profile relative to outcome. Notably, HCV persistence was associated with a reversible CD4-mediated suppression of HCV-specific CD8 T cells and with higher frequency of CD4(+)CD25(+) regulatory T cells (7.3% chronic vs. 2.5% recovered, P =.002) that could directly suppress HCV-specific type-1 CD8 T cells ex vivo. In conclusion, we found that HCV persistence is associated with a global quantitative and functional suppression of HCV-specific T cells but not differential antigenic hierarchy or cytokine phenotype relative to HCV clearance. The high frequency of CD4(+)CD25(+) regulatory T cells and their suppression of HCV-specific CD8 T cells ex vivo suggests a novel role for regulatory T cells in HCV persistence.

Two types of natriuretic peptide, atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP), very similar to each other in structure and in pharmacological effect, are known to be present in mammalian heart and brain. In our present survey for unidentified peptides in porcine brain extracts, we found a new peptide of 22 amino acid residues, eliciting a potent relaxant activity on chick rectum. The amino acid sequence determined for the peptide shows remarkable similarity to those of ANP and BNP, especially in the 17-residue sequences flanked by two cysteine residues. The peptide shows a pharmacological spectrum similar to ANP and BNP. Thus, the peptide was designated "C-type natriuretic peptide (CNP)", the third member to join the natriuretic peptide family. In contrast to ANP and BNP, CNP terminates in the second cysteine residue, lacking a further C-terminal extension.

Mitogen-activated protein kinase-activated protein kinase-1 (MAPKAP-K1; also known as p90rsk) contains two protein kinase domains in a single polypeptide. The N-terminal kinase domain is necessary for the phosphorylation of peptide substrates, whereas the C-terminal kinase domain is required for full activation of the N-terminal domain. Here we identify six sites in MAPKAP-K1a that become phosphorylated in transfected COS-1 cells. The inactive form of MAPKAP-K1a in unstimulated cells is partially phosphorylated at Ser222 and Ser733. Stimulation with phorbol 12-myristate 13-acetate induces the phosphorylation of Thr360, Ser364, Thr574, and Ser381 and increases the phosphorylation of Ser222 and Ser733. Our data indicate that mitogen-activated protein kinase activates the C-terminal kinase domain by phosphorylating Thr574 and contributes to the activation of the N-terminal kinase domain by phosphorylating Ser364. The activated C-terminal domain phosphorylates Ser381, which, together with phosphorylation of Ser364, activates the N-terminal kinase domain. The phosphorylation of Ser222 and Ser733, which can be catalyzed by the N-terminal domain, does not activate MAPKAP-K1a per se, but Ser222 phosphorylation appears to be required for activation. Ser222, Ser364, and Ser381 are situated in analogous positions to phosphorylation sites in protein kinase B, protein kinase C, and p70S6K, suggesting a common mechanism of activation for these growth factor-stimulated protein kinases.

Heat shock protein (HSP) preparations derived from cancer cells and virus-infected cells have been shown previously to elicit cancer-specific or virus-specific immunity. The immunogenicity of HSP preparations has been attributed to peptides associated with the HSPs. The studies reported here demonstrate that immunogenic HSP-peptide complexes can also be reconstituted in vitro. The studies show that (a) complexes of hsp70 or gp96 HSP molecules with a variety of synthetic peptides can be generated in vitro; (b) the binding of HSPs with peptides is specific in that a number of other proteins tested do not bind synthetic peptides under the conditions in which gp96 molecules do; (c) HSP-peptide complexes reconstituted in vitro are immunologically active, as tested by their ability to elicit antitumor immunity and specific CD8+ cytolytic T lymphocyte response; and (d) synthetic peptides reconstituted in vitro with gp96 are capable of being taken up and re-presented by macrophage in the same manner as gp96- peptides complexes generated in vivo. These observations demonstrate that HSPs are CD8+ T cell response-eliciting adjuvants.

Ca2+/CaM-dependent protein kinase II (CaM-KII) can phosphorylate and potentiate responses of alpha-amino3-hydroxyl-5-methyl-4-isoxazole-propionate-type glutamate receptors in a number of systems, and recent studies implicate this mechanism in long term potentiation, a cellular model of learning and memory. In this study we have identified this CaM-KII regulatory site using deletion and site-specific mutants of glutamate receptor 1 (GluR1). Only mutations affecting Ser831 altered the 32P peptide maps of GluR1 from HEK-293 cells co-expressing an activated CaM-KII. Likewise, when CaM-KII was infused into cells expressing GluR1, the Ser831 to Ala mutant failed to show potentiation of the GluR1 current. The Ser831 site is specific to GluR1, and CaM-KII did not phosphorylate or potentiate current in cells expressing GluR2, emphasizing the importance of the GluR1 subunit in this regulatory mechanism. Because Ser831 has previously been identified as a protein kinase C phosphorylation site (Roche, K. W., O'Brien, R. J., Mammen, A. L., Bernhardt, J., and Huganir, R. L. (1996) Neuron 16, 1179-1188), this raises the possibility of synergistic interactions between CaM-KII and protein kinase C in regulating synaptic plasticity.

Several proteins have been shown to be post-translationally modified on a specific C-terminal cysteine residue by either of two isoprenoid biosynthetic pathway metabolites, farnesyl diphosphate or geranylgeranyl diphosphate. Three enzymes responsible for protein isoprenylation were resolved chromatographically from the cytosolic fraction of bovine brain: a farnesyl-protein transferase (FTase), which modified the cell-transforming Ras protein, and two geranyl-geranyl-protein transferases, one (GGTase-I) which modified a chimeric Ras having the C-terminal amino acid sequence of the gamma-6 subunit of heterotrimeric GTP-binding proteins, and the other (GGTase-II) which modified the Saccharomyces cerevisiae secretory GTPase protein YPT1. In a S. cerevisiae strain lacking FTase activity (ram1), both GGTases were detected at wild-type levels. In a ram2 S. cerevisiae strain devoid of FTase activity, GGTase-I activity was reduced by 67%, suggesting that GGTase-I and FTase activities derive from different enzymes but may share a common genetic feature. For the FTase and the GGTase-I activities, the C-terminal amino acid sequence of the protein substrate, the CAAX box, appeared to contain all the critical determinants for interaction with the transferase. In fact, tetrapeptides with amino acid sequences identical to the C-terminal sequences of the protein substrates for FTase or GGTase-I competed for protein isoprenylation by acting as alternative substrates. Changes in the CAAX amino acid sequence of protein substrates markedly altered their ability to serve as substrates for both FTase and GGTase-I. In addition, it appeared that FTase and GGTase-I had complementary affinities for CAAX protein substrates; that is, CAAX proteins that were good substrates for FTase were, in general, poor substrates for GGTase-I, and vice versa. In particular, a leucine residue at the C terminus influenced whether a CAAX protein was either farnesylated or geranylgeranylated preferentially. The YPT1 C terminus peptide, TGGGCC, did not compete or serve as a substrate for GGTase-II, indicating that the interaction between GGTase-II and YPT1 appeared to depend on more than the 6 C-terminal residues of the protein substrate sequence. These results identify three different isoprenyl-protein transferases that are each selective for their isoprenoid and protein substrates.

OBJECTIVE

Variation within six novel genetic loci has been reported to confer risk of type 2 diabetes and may be associated with beta cell dysfunction. We investigated whether these polymorphisms are also associated with impaired proinsulin to insulin conversion.

METHODS

We genotyped 1,065 German participants for single nucleotide polymorphisms rs7903146 in TCF7L2, rs7754840 in CDKAL1, rs7923837 and rs1111875 in HHEX, rs13266634 in SLCCDKN2A/B and rs4402960 in IGF2BP2. All participants underwent an OGTT. Insulin, proinsulin and C-peptide concentrations were measured at 0, 30, 60, 90 and 120 min during the OGTT. Insulin secretion was estimated from C-peptide or insulin levels during the OGTT using validated indices. We used the ratio proinsulin/insulin during the OGTT as indicator of proinsulin conversion.

RESULTS

In our cohort, we confirmed the significant association of variants in TCF7L2, CDKAL1 and HHEX with reduced insulin secretion during the OGTT (p<0.05 for all). Variation in SLCCDKN2A/B and IGF2BP2 was not associated with insulin secretion. The risk alleles of the variants in TCF7L2, CDKAL1 and SLCCDKN2A/B and IGF2BP2 were not associated with reduced proinsulin to insulin conversion (p>0.6).

CONCLUSIONS

Diabetes-associated variants in T<em>C</em>F7L2 and <em>C</em>DKAL1 impair insulin secretion and conversion of proinsulin to insulin. However, both aspects of beta cell function are not necessarily linked, as impaired insulin secretion is specifically present in variants of HHEX and impaired proinsulin conversion is specifically present in a variant of SL<em>C</em>30A8.

BACKGROUND

The leucine zipper is a protein structural motif involved in the dimerization of a number of transcription factors. We have previously shown that peptides corresponding to the leucine-zipper region of the Fos and Jun oncoproteins preferentially form heterodimeric coiled coils, and that simple principles involving electrostatic interactions are likely to determine the pairing specificity of coiled coils. A critical test of these principles is to use them as guidelines to design peptides with desired properties.

RESULTS

Based on studies of the Fos, Jun and GCN4 leucine zippers, we have designed two peptides that are predominantly unfolded in isolation but which, when mixed, associate preferentially to form a stable, parallel, coiled-coil heterodimer. To favor heterodimer formation, we chose peptide sequences that would be predicted to give destabilizing electrostatic interactions in the homodimers that would be relieved in the heterodimer. The peptides have at least a 10(5)-fold preference for heterodimer formation, and the dissociation constant of the heterodimer in phosphate-buffered saline is approximately 30 nM at pH 7 and 20 degrees C. Studies of the pH and ionic strength dependence of stability confirm that heterodimer formation is favored largely as a result of electrostatic destabilization of the homodimers.

CONCLUSIONS

Our successful design strategy supports previous conclusions about the mechanism of interaction between the Fos and Jun oncoproteins. These results have implications for protein design, as they show that it is possible to design peptides with simple sequences that have a very high preference to pair with one another. Finally, these sequences with 'Velcro'-like properties may have practical applications, including use as an affinity reagent, in lieu of an epitope tag, or as a way of bringing together two molecules in a cell.

The solution structure of Ca(2+)-ligated calmodulin is determined from residual dipolar couplings measured in a liquid crystalline medium and from a large number of heteronuclear J couplings for defining side chains. Although the C-terminal domain solution structure is similar to the X-ray crystal structure, the EF hands of the N-terminal domain are considerably less open. The substantial differences in interhelical angles correspond to negligible changes in short interproton distances and, therefore, cannot be identified by comparison of NOEs and X-ray data. NOE analysis, however, excludes a two-state equilibrium in which the closed apo conformation is partially populated in the Ca(2+)-ligated state. The difference between the crystal and solution structures of Ca(2+)-calmodulin indicates considerable backbone plasticity within the domains of calmodulin, which is key to their ability to bind a wide range of targets. In contrast, the vast majority of side chains making up the target binding surface are locked into the same chi(1) rotameric states as in complexes with target peptide.

The activity of hypoxia-inducible transcription factor HIF, an alphabeta heterodimer that has an essential role in adaptation to low oxygen availability, is regulated by two oxygen-dependent hydroxylation events. Hydroxylation of specific proline residues by HIF prolyl 4-hydroxylases targets the HIF-alpha subunit for proteasomal destruction, whereas hydroxylation of an asparagine in the C-terminal transactivation domain prevents its interaction with the transcriptional coactivator p300. The HIF asparaginyl hydroxylase is identical to a previously known factor inhibiting HIF (FIH). We report here that recombinant FIH has unique catalytic and inhibitory properties when compared with those of the HIF prolyl 4-hydroxylases. FIH was found to require particularly long peptide substrates so that omission of only a few residues from the N or C terminus of a 35-residue HIF-1alpha sequence markedly reduced its substrate activity. Hydroxylation of two HIF-2alpha peptides was far less efficient than that of the corresponding HIF-1alpha peptides. The K(m) of FIH for O(2) was about 40% of its atmospheric concentration, being about one-third of those of the HIF prolyl 4-hydroxylases but 2.5 times that of the type I collagen prolyl 4-hydroxylase. Several 2-oxoglutarate analogs were found to inhibit FIH but with distinctly different potencies from the HIF prolyl 4-hydroxylases. For example, the two most potent HIF prolyl 4-hydroxylase inhibitors among the compounds studied were the least effective ones for FIH. It should therefore be possible to develop specific small molecule inhibitors for the two enzyme classes involved in the hypoxia response.

BACKGROUND

The liver, once fatty, overproduces components of the metabolic syndrome, such as glucose and lipids. The amount of liver fat in subjects with and without the metabolic syndrome has not been determined. It is unknown which clinically available markers best reflect liver fat content.

METHODS

Components of the metabolic syndrome as defined by the International Diabetes Federation and liver fat content by proton magnetic resonance spectroscopy were measured in 271 nondiabetic subjects (162 women, 109 men). In addition, other features of insulin resistance (serum insulin, C-peptide), intraabdominal and sc fat by magnetic resonance imaging, and liver enzymes (serum alanine aminotransferase and serum aspartate aminotransferase) were measured.

RESULTS

Liver fat was 4-fold higher in subjects with [n = 116; median 8.2% (interquartile range 3.2-18.7%)] than without [n = 155; 2.0% (1.0-5.0%); P < 0.0001] the metabolic syndrome. This increase in liver fat remained significant after adjusting for age, gender, and body mass index. All components of the metabolic syndrome correlated with liver fat content. The best correlate was waist in both women (r = 0.59, P < 0.0001) and men (r = 0.56, P < 0.0001). Liver fat correlated significantly with serum alanine aminotransferase (r = 0.39, P < 0.0001 for women; r = 0.44, P < 0.0001 for men) and aspartate aminotransferase (r = 0.27, P = 0.0005 for women; r = 0.31, P = 0.0012 for men) concentrations. The best correlates of liver fat were fasting serum insulin (r = 0.61; P < 0.0001 for both women and men) and C-peptide (r = 0.62; P < 0.0001 for both women and men).

CONCLUSIONS

Liver fat content is significantly increased in subjects with the metabolic syndrome as compared with those without the syndrome, independently of age, gender, and body mass index. Of other markers, serum C-peptide is the strongest correlate of liver fat.

OBJECTIVE

To explore the changes in serologic variables and clinical disease activity following B lymphocyte depletion in 22 patients with rheumatoid arthritis (RA).

METHODS

B lymphocyte depletion was attained using combination therapy based on the monoclonal anti-CD20 antibody rituximab. Levels of a serologic indicator of inflammation, C-reactive protein (CRP), of antimicrobial antibodies, of autoantibodies including IgA-, IgM-, and IgG-class rheumatoid factors (RF), and of antibodies to cyclic citrullinated peptide (anti-CCP) were assayed.

RESULTS

The majority of patients showed a marked clinical improvement after treatment with rituximab, with benefit lasting up to 33 months. Levels of total serum immunoglobulins fell, although the mean values each remained within the normal range. Whereas the IgM-RF response paralleled the changes in total serum IgM levels, the levels of IgA-RF, IgG-RF, and IgG and anti-CCP antibodies decreased significantly more than did those of their corresponding total serum immunoglobulin classes. The kinetics for the reduction in CRP levels also paralleled the decreases in autoantibody levels. In contrast, levels of antimicrobial antibodies did not change significantly. B lymphocyte return occurred up to 21 months posttreatment. The time to relapse after B lymphocyte return was often long and unpredictable (range 0-17 months). Relapse was, however, closely correlated with rises in the level of at least one autoantibody. Increased autoantibody levels were rarely observed in the absence of clinical change.

CONCLUSIONS

Following B lymphocyte depletion in patients with RA, a positive clinical response occurred in correlation with a significant drop in the levels of CRP and autoantibodies. Antibacterial antibody levels were relatively well maintained. B lymphocyte return preceded relapse in all patients. There was also a temporal relationship between clinical relapse and rises in autoantibody levels. Although these observations are consistent with a role for B lymphocytes in the pathogenesis of RA, the precise mechanisms involved remain unclear.