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Proprotein convertase PC5 regulation by PDGF-BB involves PI3-kinase/p70(s6)-kinase activation in vascular smooth muscle cells.

We have recently demonstrated that furin, PC5, and PC7, members of the subtilisin/kexin-like mammalian proprotein convertases (PCs), are found in rodent aorta. These PCs have been identified to activate several growth factors, adhesion molecules and extracellular matrix compounds by endoproteolytic cleavage. In the present study, we investigated the regulation of PC5 in vascular smooth muscle cells (VSMCs) in vitro and in vivo. Stimulation of rat aortic VSMCs with platelet-derived growth factor (PDGF)-BB (20 ng/mL), angiotensin II (Ang II, 1 micromol/L), or 10% fetal calf serum (FCS) for 48 hours increased DNA synthesis, as assessed by proliferating cell nuclear antigen (PCNA) immunoblotting. PC5 was strongly upregulated by PDGF-BB and 10% FCS (both 8-fold, P<0.05), whereas Ang II had no effect on PC5 protein levels compared with controls. The PCs furin and PC7, which display a comparable subcellular localization and cleavage activity, were found in VSMCs, but their levels did not increase following PDGF-BB, Ang II, or FCS stimulation. Time-course analysis revealed a rapid increase in PC5 levels after 30 minutes of PDGF-stimulation of VSMCs. PDGF-stimulated PC5 induction was inhibited by the PI3-kinase inhibitor wortmannin, and by rapamycin, an inhibitor of mTOR/p70(s6)-kinase (both P<0.05). In contrast, the mitogen-activated protein kinase (MAPK)-pathway inhibitor PD98059 did not inhibit PDGF-stimulated PC5 induction. Immunocytochemistry and in situ hybridization revealed low PC5 protein and mRNA levels in intact rat aorta in vivo. After balloon injury, PC5 protein and mRNA levels were strongly increased in proliferating PCNA-positive VSMCs. The present data demonstrate that PC5 is upregulated during proliferation of VSMCs in vivo and in vitro. We show that PDGF-induced PC5 expression is PI3-kinase/p70(s6)-kinase dependent. Thus, growth factors regulate the proprotein convertase PC5, which may play an important role during VSMC growth.

Angiotensin II↗

Selective expression of the proprotein convertases furin, pc5, and pc7 in proliferating vascular smooth muscle cells of the rat aorta in vitro.

The aim of this study was to investigate whether transformation of quiescent vascular smooth muscle cells (VSMCs) into proliferating secretory cells is accompanied by an expression of processing enzymes that activate de novo-synthesized growth factors. Three enzymes belonging to the family of the kexin/subtilisin-like mammalian proprotein convertases (PCs), furin, PC5, and PC7, were found to be upregulated after balloon denudation in vivo. To determine their importance in these cell processes, we investigated their gene regulation using a short-term organ culture system. After incubation of rat aorta for 4 and 24 hr in serum-free medium, we demonstrated a significant induction of VSMC proliferation. The affected subset of VSMCs, positive for alpha-smooth muscle actin, also expressed proliferating cell nuclear antigen (PCNA). Our results revealed a parallel upregulation of furin, PC5, and PC7 in PCNA-immunolabeled cells. As a substrate model for comparison with PCs we used nerve growth factor (NGF). NGF is known to be activated by PCs. As shown by Northern blotting analysis, NGF mRNA concentration was significantly increased in cultured explants. NGF was released into the culture medium. In conclusion, both PCs and NGF are coordinately modulated on induction of VSMC proliferation.

Animals↗

Novel putative SREBP and LXR target genes identified by microarray analysis in liver of cholesterol-fed mice.

High-cholesterol diets elicit changes in gene expression via such transcription factors as sterol-regulatory element binding proteins (SREBPs) and liver X receptors (LXRs). We used Affymetrix microarrays to identify genes in mouse liver regulated by dietary cholesterol (0.0% vs. 0.5% cholesterol wt/wt). Three independent experiments were performed, and data were analyzed with Affymetrix Microarray Suite and ANOVA statistical software. There were 69 unique Unigene clusters consistently regulated by dietary cholesterol (37 downregulated and 32 upregulated). The array results were confirmed by quantitative RT-PCR (Q-PCR) for seven of nine downregulated genes and five of six upregulated genes. A time course of dietary cholesterol feeding over 1 week revealed different temporal patterns of gene regulation for these confirmed genes. Six downregulated genes were examined in transgenic mice overexpressing truncated nuclear forms of SREBP-1a and SREBP-2, and all were induced in these mice. A second microarray analysis of mice treated with the LXR agonist TO901317 confirmed that 13 of the 32 cholesterol upregulated genes were also LXR-activated. This array result was confirmed by Q-PCR for three of three genes. In summary, these studies identified and confirmed six novel dietary cholesterol-regulated genes, three putative SREBP target genes (calcium/calmodulin-dependent protein kinase 1D, fatty acid binding protein 5, and proprotein convertase subtilisin/kexin 9), and three putative LXR target genes (a disintegrin and metalloprotease domain 11, apoptosis-inhibitory 6, and F-box-only protein 3).

Animals↗

Requirement for proprotein convertase 5/6 during decidualization of human endometrial stromal cells in vitro.

Decidualization of endometrial stromal cells (ESCs) is critical for embryo implantation and maintenance of pregnancy. Proprotein convertase (PC) 5/6 is suggested to play an important role in the processes of stromal cell decidualization and embryo implantation in the mouse. PC5/6 is a member of the PC family responsible for processing precursor proteins to their active forms by selective proteolysis. In this study, we investigated the regulation of PC5/6 mRNA and protein expression in human ESCs during decidualization in vitro. Real-time PCR analyses revealed a significant increase in PC5/6 mRNA levels in ESCs treated with 17 beta-estradiol (E(2)) plus medroxy-progesterone acetate during decidualization. On the other hand, E(2) alone did not increase PC5/6 mRNA expression. Intense PC5/6 immunoreactivity was observed in the cytoplasm of E(2) plus medroxy-progesterone acetate-treated ESCs (decidualized ESCs) compared with E(2)-treated ESCs on d 12 of culture (nondecidualized ESCs). This PC5/6 immunoreactivity was abolished by cotreatment with ZK 98299, a progesterone receptor antagonist. Western blotting revealed PC5/6 as approximately 120-kDa bands (pro- and mature forms) and a 65-kDa band (C-terminally truncated form) in decidualized ESCs. Using an antisense morpholino approach, prolactin production, a typical marker for decidualization, was significantly attenuated in decidualized ESCs after treatment with PC5/6 morpholino antisense oligonucleotides in comparison with controls. These results suggest that PC5/6 plays a key role for decidualization in human endometrium.

Cells, Cultured↗

Decidual differentiation of stromal cells promotes Proprotein Convertase 5/6 expression and lefty processing.

Lefty/Ebaf polypeptides, novel members of the TGF-beta superfamily, are involved in endometrial differentiation and embryo implantation. Recently, we showed that, during undisturbed estrous cycle, lefty is present in mouse uterine horn primarily in a precursor form. Here, we show that decidual differentiation of endometrial stroma leads to increased lefty (approximately 3.1- to 3.6-fold in vivo and 5- to 8-fold in vitro) and processing of its precursor primarily to its long form. This event occurs on d 5 of pregnancy, and is paralleled by proprotein convertase (PC)5/6 up-regulation (approximately 6-fold increase for PC5A and 3-fold increase for PC5B) in decidualized uterine horn, independent of embryo implantation. Among the known convertases, only PC5/6A processes lefty to its long form. Taken together, the findings show that decidualized differentiation of stroma, which is a prerequisite for embryo implantation, leads to processing of lefty by PC5/6A.

Animals↗

Identification of the role of a cysteine-rich region of PC6B by determining the enzymatic characteristics of its mutants.

In the proprotein convertases family, mouse PC6B (mPC6B) has a very large cysteine-rich region (CRR), consisting of 22 tandem cysteine-rich (Cys-rich) repeated segments. The role of this region remains elusive. In this report, to get insight on the possible role of the CRR, we constructed four truncated mPC6B mutant genes with 0, 5, 11, and 22 Cys-rich repeated segments remaining; using the baculovirus-expression system and a simple purification method, we obtained four enzyme mutants of mPC6B. By determining their optimal pH and calcium ion concentration for enzymatic activity and their thermal stability, we found that CRR did not affect pH optimum and Ca2+ optimum compared with the p-domain. However, CRR acted as a stabilizing domain in addition to the p-domain. By kinetic analyses of four mutants, we found that the long Cys-rich repeats in the native form of mPC6B reduced its Vmax. These facts suggest that CRR acts as an important part of functional domain.

Animals↗

Chromosomal assignments of the genes for neuroendocrine convertase PC1 (NEC1) to human 5q15-21, neuroendocrine convertase PC2 (NEC2) to human 20p11.1-11.2, and furin (mouse 7[D1-E2] region).

The chromosomal localization of the genes coding for the pro-protein and pro-hormone convertases PC1, PC2, and Furin has been achieved by in situ hybridization. The genes for PC1 and PC2 were located on human chromosomes 5q15-21 and 20p11.1-11.2, respectively. The gene for Furin was assigned to the mouse chromosome 7D1-7E2 region. These data complete the chromosomal localization of these three convertases in both human and mouse. The results confirm the regional correspondence of the human chromosomes 15 and mouse chromosomes 7, as well as between human chromosome 20 and mouse chromosome 2. Furthermore, the identification of the NEC1 locus on human chromosome 5 and mouse chromosome 13 suggests a conservation of synthenic regions between these regions of the human and mouse genomes.

Animals↗

Cross-Ancestry Proteogenomic Analyses Identified New Therapeutic Insights for Ischemic Heart Disease.

BACKGROUND: Most drugs target proteins, and proteome-wide genetic analyses in diverse populations could discover potential novel and repurposed targets for improved prevention and treatment of ischemic heart disease (IHD) beyond statin therapy. OBJECTIVES: The purposes of this study were to use cis-acting single nucleotide polymorphisms (cis-pQTLs) identified for plasma proteins in East Asians and Europeans to discover and validate potential drug targets for IHD. METHODS: We measured plasma levels of 9,520 (Olink/SomaScan: 2,923/7,297) proteins in a case-cohort study of IHD (1,976 incident cases and 2,001 subcohort controls) in statin-free individuals in the prospective China Kadoorie Biobank (CKB). Genome-wide association studies identified 2,895 (Olink/SomaScan: 1,301/1,594) cis-pQTLs for these proteins in CKB. Two-sample Mendelian randomization (MR) and colocalization analyses assessed associations of all available cis-pQTLs for these proteins with IHD in East Asians (n = 29,319 cases), with further replication in Europeans (n = 181,522 cases) and comparison with findings in previous MR studies. RESULTS: In CKB observational analyses, a total of 959 (Olink/SomaScan: 426/533) proteins were associated at false discovery rate-corrected P < 0.05 with IHD after adjusting for major IHD risk factors. Two-sample MR analyses provided genetic support for 54 unique (Olink/SomaScan: 36/28) proteins in IHD etiology. Colocalization analyses confirmed shared gene-protein-IHD associations (posterior probability of hypothesis 4 [PPH4] &#x2265;0.8) for 15 unique (Olink/SomaScan: 10/10) proteins, including 8 lipid-related, 3 inflammation-related, 1 blood pressure-related, and 3 alcohol-related proteins in East Asians. In Europeans, MR analyses of 12 non-alcohol-related proteins showed directionally concordant results for 8 proteins, with 5 having strong colocalization evidence of shared gene-protein-IHD associations (PPH4 &#x2265;0.8), including 4 lipid-related (proprotein convertase subtilisin/kexin type 9, LPA, APOE, cadherin-1) and 1 systolic blood pressure-related (fibroblast growth factor 5) protein. However, 4 proteins showed directionally discordant MR results, including 2 lipid-related (APOA5, SORT1) and 1 inflammation-related (transforming growth factor beta 1) proteins with strong colocalization evidence of shared gene-protein-IHD associations (PPH4 &#x2265;0.8). Comparison with previous MR studies revealed little consistency across studies in the number and identity of target proteins for IHD beyond well-established lipid-related (low-density lipoprotein cholesterol, lipoprotein(a), and triglycerides) or inflammation-related (interleukin-6) protein targets. CONCLUSIONS: The findings support a role for lipid-driven chronic inflammation in IHD etiology, and treatment strategies simultaneously targeting multiple lipid and inflammation pathways should be prioritized for further research to improve drug treatment of IHD beyond statin therapy.

Aged↗

A novel mechanism for localizing membrane proteins to yeast trans-Golgi network requires function of synaptojanin-like protein.

Localization of resident membrane proteins to the yeast trans-Golgi network (TGN) involves both their retrieval from a prevacuolar/endosomal compartment (PVC) and a "slow delivery" mechanism that inhibits their TGN-to-PVC transport. A screen for genes required for the slow delivery mechanism uncovered INP53, a gene encoding a phosphoinositide phosphatase. A retrieval-defective model TGN protein, A(F-->A)-ALP, was transported to the vacuole in inp53 mutants approximately threefold faster than in wild type. Inp53p appears to function in a process distinct from PVC retrieval because combining inp53 with mutations that block retrieval resulted in a much stronger phenotype than either mutation alone. In vps27 strains defective for both anterograde and retrograde transport out of the PVC, a loss of Inp53p function markedly accelerated the rate of transport of TGN residents A-ALP and Kex2p into the PVC. Inp53p function is cargo specific because a loss of Inp53p function had no effect on the rate of Vps10p transport to the PVC in vps27 cells. The rate of early secretory pathway transport appeared to be unaffected in inp53 mutants. Cell fractionation experiments suggested that Inp53p associates with Golgi or endosomal membranes. Taken together, these results suggest that a phosphoinositide signaling event regulates TGN-to-PVC transport of select cargo proteins.

Alkaline Phosphatase↗

Proprotein convertase PACE4 is down-regulated by the basic helix-loop-helix transcription factor hASH-1 and MASH-1.

PACE4 is a mammalian subtilisin-like proprotein convertase that activates transforming growth factor (TGF)-beta-related proteins such as bone morphogenetic protein 2 (BMP2), BMP4 and Nodal and exhibits a dynamic expression pattern during embryogenesis. We recently determined that the 1 kb 5'-upstream region of the PACE4 gene contains 12 E-box (E1-E12) elements and that an E-box cluster (E4-E9) acts as a negative regulator [Tsuji, Yoshida, Hasegawa, Bando, Yoshida, Koide, Mori and Matsuda (1999) J. Biochem. (Tokyo) 126, 494-502]. It is known that the mammalian achaete-scute homologue 1 (MASH-1) binds specifically to an E-box (CACCTG) sequence in collaboration with E47, a ubiquitously expressed basic helix-loop-helix (bHLH) factor. To identify the roles of the bHLH factor and E-box elements in regulating PACE4 gene expression in neural development, we analysed the effects of human achaete-scute homologue 1 (hASH-1) on PACE4 gene expression with various neuroblastoma cell lines. The expressions of PACE4 and hASH-1 are correlated inversely in these cell lines. The overexpression of hASH-1 or MASH-1 causes a marked decrease in endogenous PACE4 gene expression but has no effect on the expression of other subtilisin-like proprotein convertases such as furin, PC5/6 and PC7/8. In contrast, other neural bHLH factors (MATH-1, MATH-2, neurogenin 1, neurogenin 2, neurogenin 3 and E47) did not affect PACE4 gene expression. Furthermore, an E-box cluster was a negative regulatory element for the promoter activity in NBL-S cells expressing hASH-1 at high level as determined by a luciferase assay. Binding of hASH-1 to the E-box cluster was confirmed by gel mobility-shift assay. In the present study we identified the PACE4 gene as one of the targets of hASH-1, which is a key factor in the initiation of neural differentiation. These results suggest that the alteration of PACE4 gene expression by hASH-1 causes rapid changes in the biological activities of TGF-beta-related proteins via post-translational modification of these proteins.

Basic Helix-Loop-Helix Proteins↗

Expression of proprotein convertase 2 mRNA in the ovarian follicles of the medaka, Oryzias latipes.

Proprotein convertases (PCs) are enzymes responsible for processing the precursors of many bioactive peptides in vertebrates and invertebrates. In the present study, a cDNA for proprotein convertase 2 (PC2) was cloned for the first time from a fish. The clone, which was isolated from the ovary of the medaka, Oryzias latipes, by a combination of RT-PCR cloning and 5'- and 3'-rapid amplification of cDNA ends, codes for a protein of 641 amino acid residues highly homologous to other vertebrate PC2. The medaka preproPC2 consists of a signal sequence, a propeptide with sites for autocatalytic activation, a Kex2-like catalytic domain, and a P-domain. The catalytic triad residues (Asp-169, His-210, and Ser-386) were all conserved. Northern blot analysis revealed that PC2 was expressed in the brain, ovary, and kidney of the fish. The size of PC2 mRNA expressed in the ovary was 2.3 kb, whereas those of the brain and kidney were 2.8 kb. This size difference was attributed to the lack of an approximately 300-bp nucleotide sequence just before the poly(A)+ tail of the ovarian PC2 mRNA. Ovarian expression of the PC2 gene was found in the medaka but not in the mouse, and therefore further analysis was conducted for the fish ovary. The greatest expression of PC2 mRNA in the oocytes of small growing follicles in the mature medaka was demonstrated by Northern blotting, RT-PCR and in situ hybridization analysis. These results suggest that PC2 may play a role in the processing of proproteins and/or pro-hormones expressed in the growing oocytes.

Amino Acid Sequence↗

Molecular diversity in neurosecretion: reflections on the hypothalamo-neurohypophysial system.

1. The diversity of molecules involved in various aspects of neurosecretion, such as proprotein processing, axonal transport of large dense core vesicles (LDCVs), and regulated secretion, is discussed in the context of the hypothalamo-neurohypophysial system (HNS). 2. Recent studies have uncovered a family of at least seven processing enzymes known as proprotein convertases (PCs) which are involved in proteolytically cleaving protein precursors at paired basic amino acid motifs to yield biologically active peptides. Three of these, PC1(3), 2, and 5, are found in neurons and are involved in producing regulated secretory peptide products. 3. The axonal transport of LDCVs occurs on microtubule tracks by still unknown mechanisms. There are over 11 distinct kinesin-related molecules that have now been identified as possible microtubule motor candidates. 4. Calcium channels in the nervous system are known to be derived from at least five alpha-subunit and four beta-subunit genes with multiple alternatively spliced isoforms in each case. These could account, in part, for the varied calcium currents found in the HNS. 5. The large number of proteins and isoforms now demonstrated to be involved in regulated secretion are discussed, with a focus on LDCV compositions and the synaptotagmin gene family.

Animals↗

Biosynthetic processing of the pro-alpha 1(V)2pro-alpha 2(V) collagen heterotrimer by bone morphogenetic protein-1 and furin-like proprotein convertases.

The low abundance fibrillar collagen type V is incorporated into and regulates the diameters of type I collagen fibrils. Bone morphogenetic protein-1 (BMP-1) is a metalloprotease that plays key roles in regulating formation of vertebrate extracellular matrix; it cleaves the C-propeptides of the major fibrillar procollagens I-III and processes precursors to produce the mature forms of the cross-linking enzyme prolysyl oxidase, the proteoglycan biglycan, and the basement membrane protein laminin 5. Here we have successfully produced recombinant pro-alpha1(V)(2)pro-alpha2(V) heterotrimers, and we have used these to characterize biosynthetic processing of the most prevalent in vivo form of type V procollagen. In addition, we have compared the processing of endogenous pro-alpha1(V) chains by wild type mouse embryo fibroblasts and by fibroblasts derived from embryos doubly homozygous null for the Bmp-1 gene and for a gene encoding the closely related metalloprotease mammalian Tolloid-like 1. Together, results presented herein indicate that within pro-alpha1(V)(2)pro-alpha2(V) heterotrimers, pro-alpha1(V) N-propeptides and pro-alpha2(V) C-propeptides are processed by BMP-1-like enzymes, and pro-alpha1(V) C-propeptides are processed by furin-like proprotein convertases in vivo.

Amino Acid Sequence↗

Nucleotide sequence and analysis of the mouse SPC3 promoter region.

Insulin is converted from the higher molecular weight proprotein, proinsulin by highly specific proteolytic cleavage at two dibasic amino acid sites. SPC3 and SPC2, two recently identified prohormone convertase that are specifically expressed in beta cells and other neuroendocrine cells, appear to be responsible for those cleavages. We have sequenced the 5'-upstream region of the SPC3 gene and examined its promotor/enhancer activity and most of several deletion mutants in several cell lines. This region contains no CAAT box but has several non-functional TATA-like sequences and several putative transcriptional regulatory elements, including AP-1, Sp1 and cAMP response elements. These features are not unlike those of the human SPC2 upstream region. In beta TC3 insulinoma cells, the sequence between the EcoRI (620 bp) and NsiI (702 bp) sites seems to be important for gene expression, while the sequence between the NsiI and DraI (775 bp) sites may contain strong enhancer element(s).

Amino Acid Sequence↗

Genetic polymorphisms that predict outcome and need for treatment in cardiovascular disease.

PURPOSE OF REVIEW: Interest in the genetic determinants of complications of cardiovascular disease, and the resultant influence on management, has increased. We have therefore reviewed the literature in the last 12-16 months for studies documenting genetic risk of complications. The focus is on risk of complications or differences in management, rather than only susceptibility to cardiovascular disease itself. RECENT FINDINGS: Polymorphisms in myocyte enhancer factor 2A, a transcription factor, tumor necrosis factor (ligand) superfamily, member 4, the OX40 ligand, and proprotein convertase subtilisin/kexin type 9, which affect low-density lipoprotein levels, have all been associated with an altered risk of coronary artery disease and myocardial infarction. A preliminary study of genotype-specific therapy of the 5-lipoxygenase pathway has shown benefit in the intermediate endpoint of reduction in inflammatory markers in patients at risk of myocardial infarction and stroke. Bleeding and renal complications after coronary artery bypass surgery have also been associated with genetic polymorphisms. A familial study confirms a genetic association with thoracic aortic aneurysms. SUMMARY: A familial risk of cardiovascular disease is well known. The specific genotypes at risk are increasingly being discovered. The science has progressed to the point that genotype-specific interventions are increasingly feasible.

Cardiovascular Diseases↗

Structure and expression of Furin mRNA in the ovary of the medaka, Oryzias latipes.

A cDNA for furin was cloned from the ovary of the medaka, Oryzias latipes, by a combination of cDNA library screening, 5'-rapid amplification of cDNA ends (RACE), and 3'- RACE. The cDNA sequence codes for a protein of 814 amino acid residues highly homologous to other vertebrate furins, Ca(2+)-dependent serine proteases belonging to the subtilysin-like proprotein convertase family. The medaka preprofurin consists of a leader sequence, a propeptide with autoactivation sites, a Kex2-like catalytic domain, a P domain, a cysteine-rich domain, a putative transmembrane domain, and a cytoplasmic domain. The catalytic triad residues (Asp-164, His-205, and Ser-379) were all conserved. Furin mRNA was expressed in many tissues of this, including the ovary. In the ovary, the greatest expression of furin mRNA occurred in oocytes of small growing follicles, as demonstrated by Northern blotting, RT-PCR, and in situ hybridization analysis. Temporary and spatial expression patterns of the medaka fish furin were similar to those of stromelysin-3 and MT5-MMP during oocyte growth and postnatal development.

Amino Acid Sequence↗