Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Following the cleavage of peptide precursors by endopeptidases such as the proprotein convertases PC2 and PC3, carboxypeptidase E (CPE) functions to remove basic amino adds from the C-terminus of various pituitary hormones. We investigated the role of CPE in the differential sensitivity between rat strains to estrogen-induced pituitary tumors. Pituitary CPE protein levels were unchanged by diethylstilbestrol (DES) in tumor-resistant Sprague-Dawley (SD) rats. However, in tumor-susceptible Fischer 344 (F344) rats, DES decreased CPE protein levels such that by 7 and 8 weeks of treatment, CPE was barely detectable. One week withdrawal of DES caused an increase in CPE protein levels at 8 weeks. After 2 and 4 weeks of DES treatment, CPE protein levels in F344 rats decreased to 18 and 2.3% of control values, respectively, but no strain difference was observed in the protein levels of proprotein convertase 2 (PC2) or PC3. Additionally, Brown Norway (BN), F344, and F1 hybrid (BN x F344) rats were treated with DES for 10 weeks. The level of pituitary CPE protein was not affected by DES in BN rats whereas F344 rats had only 8% of the level of CPE pituitary protein of BN rats. The pituitaries of F1 rats, which had an intermediate weight response to DES, had an intermediate level of CPE protein (31% that of BN rats). Levels of CPE mRNA were not affected by DES in SD rats while in F344 rats DES tended to decrease levels of CPE mRNA after both 2 and 4 weeks of treatment, although the response was variable. It thus appears that pituitary CPE protein is differentially regulated by DES between tumor-resistant rats and F344 rats primarily at the post-transcriptional level. Furthermore, in F344 rats, levels of CPE protein are inversely correlated to increases in pituitary weight caused by DES treatment.
Mol Cell Endocrinol 1996 Mar 25
PMID:Decreased expression of carboxypeptidase E protein is correlated to estrogen-induction of rat pituitary tumors. 873 83

The tubby strain of mice exhibits maturity-onset obesity and sensory deficits in vision and hearing. The mutated gene, tub , responsible for this phenotype was identified recently, but the function of the TUB protein has not been deduced from its amino acid sequence. This prompted us to undertake expression mapping studies with the hope that they might help to elucidate the biological role of the TUB protein. We report the tub gene expression pattern in embryonic, fetal and adult mice tissues as determined by northern blots and in situ hybridization, using antisense oligonucleotidic probes. In mouse embryos, tub is expressed selectively in differentiating neurons of the ensemble of central and peripheral nervous systems, starting at 9.5 days after conception. In adult mice, tub is transcribed in several major brain areas, including cerebral cortex, hippocampus, several nuclei of the hypothalamus controlling feeding behavior, in the spiral ganglion of the inner ear and in the photoreceptor cells of the retina. These structures contain potential cellular targets of the tubby mutation-induced pathogenesis. The neuronal-specific tub gene distribution allows the establishment of a genotype-phenotype correlation in the tubby mice. This correlation is reminiscent of that observed in fat/fat mice, whose phenotype, also characterized by obesity, is caused by a null mutation in the carboxypeptidase E (CPE) gene. Our observations highlight similarities between CPE, prohormone convertases, several neuropeptides and tub gene expression patterns during embryogenesis, and may narrow down the avenues to explore in order to determine ultimately the function of the TUB protein.
Hum Mol Genet 1998 Sep
PMID:Prominent neuronal-specific tub gene expression in cellular targets of tubby mice mutation. 970 Jan 99

We have previously reported that membrane-bound aminopeptidases were expressed on human follicles and corpora lutea (CL) and we showed that these aminopeptidases are involved in follicular growth, probably by regulating extracellular peptide concentrations. In this study, the expression of membrane-bound carboxypeptidase-M (CP-M), which cleaves carboxyl-terminal amino acids from peptides extracellularly, on human follicles and CL was examined. In growing and pre-ovulatory follicles, CP-M was immunohistochemically detected with weak or moderate intensity on theca interna cells. Although CP-M was not detected on granulosa cells in growing and pre-ovulatory follicles, it was strongly detected on the cell surface of luteinizing granulosa cells isolated from patients undergoing in-vitro fertilization treatment, indicating that CP-M was rapidly expressed on granulosa cells during ovulation. In menstrual and pregnant CL, CP-M was clearly detected on luteal cells. In menstrual CL, the expression of CP-M mRNA was observed by reverse transcription-polymerase chain reaction (RT-PCR). Western blotting analysis revealed that the molecular mass of the CP-M extracted from mid-luteal CL was 62 kDa. These results indicate that CP-M is a cell surface differentiation-related molecule of human granulosa, theca, and luteal cells. The rapid expression on granulosa cells during ovulation strongly suggests the involvement of CP-M in the ovulation and CL formation processes.
Mol Hum Reprod 1998 Jul
PMID:Membrane-bound carboxypeptidase-M is expressed on human ovarian follicles and corpora lutea of menstrual cycle and early pregnancy. 970 94

The binding of pro-opiomelanocortin,(POMC), pro-insulin, pro-enkephalin and chromogranin A (CGA) to the regulated secretory pathway sorting receptor, carboxypeptidase E (CPE), in bovine pituitary secretory granule (SG) membranes was investigated. N-POMC1-26, which contains the POMC sorting signal, bound to CPE in the SG membranes with low affinity and the binding was ion independent. Pro-insulin bound CPE with similar kinetics. Pro-enkephalin, but not CGA bound to CPE with similar IC50 as pro-insulin and N-POMC1-26. Crosslinking studies showed that pro-insulin and pro-enkephalin bound specifically to SG membrane CPE, similar to N-POMC1-26 reported previously. CPE was extracted from the SG membranes with NaHCO3 or KSCN, but not Triton X-100/1 M NaCl. The results show that CPE is tightly associated with SG membranes and binds several prohormones, but not CGA, with similar kinetics, providing further evidence that membrane CPE has the characteristics to function as a common sorting receptor for targeting prohormones to the regulated secretory pathway.
Mol Cell Endocrinol 1998 Apr 30
PMID:Carboxypeptidase E is a sorting receptor for prohormones: binding and kinetic studies. 970 69

Sorting of the prohormone POMC to the regulated secretory pathway necessitates the binding of a sorting signal to a sorting receptor, identified as membrane carboxypeptidase E (CPE). The sorting signal, located at the N terminus of POMC consists of two acidic (Asp10, Glu14) and two hydrophobic (Leu11, Leu18) residues exposed on the surface of an amphipathic loop. In this study, molecular modeling of CPE predicted that the acidic residues in the POMC-sorting signal bind specifically to two basic residues, Arg255 and Lys260, present in a loop unique to CPE, compared with other carboxypeptidases. To test the model, these two residues on CPE were mutated to Ser or Ala, followed by baculovirus expression of the mutant CPEs in Sf9 cells. Sf9 cell membranes containing CPE mutants with either Arg255 or Lys260, or both residues substituted, showed no binding of [125I]N-POMC1-26 (which contains the POMC-sorting signal motif), proinsulin, or proenkephalin. In contrast, substitution of an Arg147 to Ala147 at a substrate-binding site, Arg259 to Ala259 and Ser202 to Pro202, in CPE did not affect the level of [125I]N-POMC1-26 binding when compared with-wild type CPE. Furthermore, mutation of the POMC-sorting signal motif (Asp10, Leu11, Glu14, Leu18) eliminated binding to wild-type CPE. These results indicate that the sorting signal of POMC, proinsulin, and proenkephalin specifically interacts with Arg255 and Lys260 at a novel binding site, independent of the active site on CPE.
Mol Endocrinol 1999 Apr
PMID:Identification of a novel prohormone sorting signal-binding site on carboxypeptidase E, a regulated secretory pathway-sorting receptor. 1019 59

Recently, two different prohormone-processing enzymes, prohormone convertase 1 (PC1) and carboxypeptidase E, have been implicated in enhancing the storage of peptide hormones in endocrine secretory granules. It is important to know the extent to which such molecules may act as "sorting receptors" to allow the selective trafficking of cargo proteins from the trans-Golgi network into forming granules, versus acting as enzymes that may indirectly facilitate intraluminal storage of processed hormones within maturing granules. GH4C1 cells primarily store prolactin in granules; they lack PC1 and are defective for intragranular storage of transfected proinsulin. However, proinsulin readily enters the immature granules of these cells. Interestingly, GH4C1 clones that stably express modest levels of PC1 store more proinsulin-derived protein in granules. Even in the presence of PC1, a sizable portion of the proinsulin that enters granules goes unprocessed, and this portion largely escapes granule storage. Indeed, all of the increased granule storage can be accounted for by the modest portion converted to insulin. These results are not unique to GH4C1 cells; similar results are obtained upon PC1 expression in PC12 cells as well as in AtT20 cells (in which PC1 is expressed endogenously at higher levels). An in vitro assay of protein solubility indicates a difference in the biophysical behavior of proinsulin and insulin in the PC1 transfectants. We conclude that processing to insulin, facilitated by the catalytic activities of granule proteolytic enzymes, assists in the targeting (storage) of the hormone.
Mol Biol Cell 2000 Jun
PMID:Proinsulin endoproteolysis confers enhanced targeting of processed insulin to the regulated secretory pathway. 1084 22

One of the most common mechanisms of posttranslational modifications to generate biologically active (neuro)peptides is the process of peptide alpha-amidation. The only enzyme known to catalyze this important modification is peptidylglycine alpha-amidating monooxygenase (PAM): a (bifunctional) zymogen, giving rise to a monooxygenase (PHM) and a lyase (PAL). The highly peptidergic central nervous system and endocrine system of the marine mollusk Aplysia has homologs of various mammalian peptide processing enzymes, including furin, Afurin2, prohormone convertase 1 (PC1), PC2, carboxypeptidase E (CPE) and CPD. Previously, it has been shown that the abdominal ganglion of Aplysia, which contains approximately 800 peptidergic bag cell neurons, contains the highest specific alpha-amidating activity. We have identified and cloned multiple overlapping central nervous system and bag cell cDNAs that encode a predicted 748-residue protein that is a member of the PAM family. The protein sequence contains the contiguous sequence of the catalytic domains of PHM and PAL, clearly demonstrating the existence of bifunctional Aplysia PAM, the first invertebrate PAM zymogen with an organization similar to that in vertebrates. None of the characterized clones encoded the so-called exon A domain between the PHM and PAL domains. Furthermore, in a specific search by reverse transcription-polymerase chain reaction of RNA from multiple tissues we could only detect exon A-less transcripts. PAM expression was detected in the central nervous system, and in several endocrine and exocrine organs. Aplysia PAM is a candidate prohormone processing enzyme that plays an important role in the processing of Aplysia prohormones in the secretory pathway.
Brain Res Mol Brain Res 2000 Oct 20
PMID:Neuropeptide amidation: cloning of a bifunctional alpha-amidating enzyme from Aplysia. 1104 55

Our recent published studies suggest that angiotensin II (AII), generated and retained intracellularly, enhances growth of H4-II-E-C3 rat hepatoma cells, an average of 33%. Proliferation conferred by introduction of a plasmid [ Ang(-S)Exp/pSVL ] encoding a signal sequence-depleted angiotensinogen [Ang(-S)Exp] into these cells (which we have shown possess ACE and renin mRNAs) is mediated, at least in part, by enhanced PDGF-A chain mRNA production and protein secretion. The mitogenic effect is inhibited by losartan suggesting that it involves AII interaction with an AT(1)-like receptor. Introduction of anti-AII antibodies into the medium of these transfected cells has no effect upon growth of the cells, suggesting that AII is retained by the cells and that intracellular AII is growth stimulatory. In the present study, we sought to further characterize the intracellular localization and mode of action of Ang(-S)Exp. Consistent with our expectations, we now show that a fusion product of Ang(-S)Exp with green fluorescent protein [Ang(-S)Exp/EGFP], generated from an expression plasmid, is abundant and primarily cytoplasmic. Wild-type angiotensinogen/EGFP, in contrast, is only detectable following a cold-block (which acts to enhance folding-kinetics and slow secretion) and is largely restricted to the secretory pathway. We further show, using semi-quantitative RT/PCR that the long isoform of PDGF mRNA is elevated in Ang(-S)Exp transfected cells and in AII-treated naive cells but not in losartan-treated Ang(-S)Exp transfected cells. We identify C-terminal amidation recognition sites within the long-form protein (that are not present in the short-form) and show that these cells possess PAM (amidating enzyme precursor) and carboxypeptidase E mRNAs (the corresponding proteins of which are sufficient for amidation). Inhibitors of amidation inhibit growth of naive and Ang(-S)Cntr/ pSVL -transfected cells (2.6-fold for phenylbutenoic acid and 3.5-fold for disulfiram treatment) but more profoundly inhibit growth of Ang(-S)Exp/pSVL -transfected cells (6.7-fold for phenylbutenoic acid and 13-fold for disulfiram). In conclusion, these data confirm that signal sequence-depleted Ang(-S)Exp is retained within cells and is largely cytoplasmic. Because C-terminal amidation is absolutely required for full biological potency of a number of peptide hormones (including oxytocin, gastrin and calcitonin), we postulate that growth effects of both intracellular AII and exogenous AII can be conferred by PDGF long-form, possibly through an amidation-dependent mechanism.
J Mol Cell Cardiol 2002 Nov
PMID:Intracellular angiotensin II increases the long isoform of PDGF mRNA in rat hepatoma cells. 1243 51

The aim of this study was to identify candidate genes for visceral obesity by screening for genes strongly differentially expressed between human subcutaneous and visceral adipose depots. A cDNA microarray with human adipose-derived cDNAs was used as an initial screening to identify genes that are potentially differentially expressed between human subcutaneous and visceral abdominal fat tissues. For the two best candidates, carboxypeptidase E (CPE) and thrombospondin-1 (THBS1) (EST N72406), real-time RT-PCR was performed to confirm their depot specific expression in extremely obese individuals. Both genes appeared to be strongly differentially expressed, having a higher expression in the visceral depot than in the subcutaneous one. For THBS1, the difference in expression between the depots was greater in women than in men. The involvement of CPE and THBS1 in obesity allows us to suggest that the physiological processes controlled by these genes contribute to depot and gender-related differences in the metabolic complications of obesity.
Cell Mol Life Sci 2002 Nov
PMID:Carboxypeptidase E and thrombospondin-1 are differently expressed in subcutaneous and visceral fat of obese subjects. 1253 May 26

In familial hyperproinsulinemia, specific mutations in the proinsulin gene are linked with a profound increase in circulating plasma proinsulin levels. However, the molecular and cellular basis for this disease remains uncharacterized. Here we investigated how these mutations may disrupt the sorting signal required to target proinsulin to the secretory granules of the regulated secretory pathway, resulting in the unregulated release of proinsulin. Using a combination of molecular modeling and site-directed mutagenesis, we have identified structural molecular motifs in proinsulin that are necessary for correct sorting into secretory granules of endocrine cells. We show that membrane carboxypeptidase E (CPE), previously identified as a prohormone-sorting receptor, is essential for proinsulin sorting. This was demonstrated through short interfering RNA-mediated depletion of CPE and transfection with a dominant negative mutant of CPE in a beta-cell line. Mutant proinsulins found in familial hyperproinsulinemia failed to bind to CPE and were not sorted efficiently. These findings provide evidence that the elevation of plasma proinsulin levels found in patients with familial hyperproinsulinemia is caused by the disruption of CPE-mediated sorting of mutant proinsulins to the regulated secretory pathway.
Mol Endocrinol 2003 Sep
PMID:Disruption of a receptor-mediated mechanism for intracellular sorting of proinsulin in familial hyperproinsulinemia. 1282 4


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