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Mammalian subtilisin/kexin isozyme SKI-1: A widely expressed proprotein convertase with a unique cleavage specificity and cellular localization.

ABSTRACT: Using reverse transcriptase-PCR and degenerate oligonucleotides derived from the active-site residues of subtilisin/kexin-like serine proteinases, we have identified a highly conserved and phylogenetically ancestral human, rat, and mouse type I membrane-bound proteinase called subtilisin/kexin-isozyme-1 (SKI-1). Computer databank searches reveal that human SKI-1 was cloned previously but with no identified function. In situ hybridization demonstrates that SKI-1 mRNA is present in most tissues and cells. Cleavage specificity studies show that SKI-1 generates a 28-kDa product from the 32-kDa brain-derived neurotrophic factor precursor, cleaving at an RGLT downward arrowSL bond. In the endoplasmic reticulum of either LoVo or HK293 cells, proSKI-1 is processed into two membrane-bound forms of SKI-1 (120 and 106 kDa) differing by the nature of their N-glycosylation. Late along the secretory pathway some of the membrane-bound enzyme is shed into the medium as a 98-kDa form. Immunocytochemical analysis of stably transfected HK293 cells shows that SKI-1 is present in the Golgi apparatus and within small punctate structures reminiscent of endosomes. In vitro studies suggest that SKI-1 is a Ca2+-dependent serine proteinase exhibiting a wide pH optimum for cleavage of pro-brain-derived neurotrophic factor.

SUBMITTER: Seidah NG

PROVIDER: S-EPMC15461 | biostudies-literature | 1999 Feb

REPOSITORIES: biostudies-literature

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Mammalian subtilisin/kexin isozyme SKI-1: A widely expressed proprotein convertase with a unique cleavage specificity and cellular localization.

Seidah N G NG Mowla S J SJ Hamelin J J Mamarbachi A M AM Benjannet S S Touré B B BB Basak A A Munzer J S JS Marcinkiewicz J J Zhong M M Barale J C JC Lazure C C Murphy R A RA Chrétien M M Marcinkiewicz M M

Proceedings of the National Academy of Sciences of the United States of America 19990201 4

Using reverse transcriptase-PCR and degenerate oligonucleotides derived from the active-site residues of subtilisin/kexin-like serine proteinases, we have identified a highly conserved and phylogenetically ancestral human, rat, and mouse type I membrane-bound proteinase called subtilisin/kexin-isozyme-1 (SKI-1). Computer databank searches reveal that human SKI-1 was cloned previously but with no identified function. In situ hybridization demonstrates that SKI-1 mRNA is present in most tissues an ...[more]

PMID: 9990022

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Project description:Proprotein convertase subtilisin/kexins (PCSKs) constitute a family of nine related proteases: PCSK1-7, MBTPS1, and PCSK9. Apart from PCSK9, little is known about PCSKs in cardiovascular disease. Here, we aimed to investigate the expression landscape and druggability potential of the entire PCSK family for CVD. We applied an integrative approach, combining genetic, transcriptomic and proteomic data from three vascular biobanks comprising carotid atherosclerosis, thoracic and abdominal aneurysms, with patient clinical parameters and immunohistochemistry of vascular biopsies. Apart from PCSK4, all PCSK family members lie in genetic regions containing variants associated with human cardiovascular traits. Transcriptomic analyses revealed that FURIN, PCSK5, MBTPS1 were downregulated, while PCSK6/7 were upregulated in plaques vs. control arteries. In abdominal aneurysms, FURIN, PCSK5, PCSK7, MBTPS1 were downregulated, while PCSK6 was enriched in diseased media. In thoracic aneurysms, only FURIN was significantly upregulated. Network analyses of the upstream and downstream pathways related to PCSKs were performed on the omics data from vascular biopsies, revealing mechanistic relationships between this protein family and disease. Cell type correlation analyses and immunohistochemistry showed that PCSK transcripts and protein levels parallel each other, except for PCSK9 where transcript was not detected, while protein was abundant in vascular biopsies. Correlations to clinical parameters revealed a positive association between FURIN plaque levels and serum LDL, while PCSK6 was negatively associated with Hb. PCSK5/6/7 were all positively associated with adverse cardiovascular events. Our results show that PCSK6 is abundant in plaques and abdominal aneurysms, while FURIN upregulation is characteristic for thoracic aneurysms. PCSK9 protein, but not the transcript, was present in vascular lesions, suggesting its accumulation from circulation. Integrating our results lead to the development of a novel 'molecular' 5D framework. Here, we conducted the first integrative study of the proprotein convertase family in this context. Our results using this translational pipeline, revealed primarily PCSK6, followed by PCSK5, PCSK7 and FURIN, as proprotein convertases with the highest novel therapeutic potential.

Dataset Information

Mammalian subtilisin/kexin isozyme SKI-1: A widely expressed proprotein convertase with a unique cleavage specificity and cellular localization.

Publications

Mammalian subtilisin/kexin isozyme SKI-1: A widely expressed proprotein convertase with a unique cleavage specificity and cellular localization.

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