Mammalian subtilisin/kexin isozyme SKI-1: A widely expressed proprotein convertase with a unique cleavage specificity and cellular localization.
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.
Seidah
N G
NG
Laboratory of Biochemical, Clinical Research Institute of Montreal, 110 Pine Avenue West, Montreal, QC, Canada H2W 1R7.
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
D000595:Amino Acid Sequence; D000818:Animals; D000831:Animals, Newborn; D002460:Cell Line; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D008322:Mammals; D051379:Mice; D008969:Molecular Sequence Data; D008970:Molecular Weight; D009928:Organ Specificity; D016133:Polymerase Chain Reaction; D043484:Proprotein Convertases; D011498:Protein Precursors / Q000378:metabolism; D011499:Protein Processing, Post-Translational; D012333:RNA, Messenger / Q000235:genetics; D051381:Rats; D017207:Rats, Sprague-Dawley; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D013379:Substrate Specificity; D013381:Subtilisins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D014158:Transcription, Genetic; D014162:Transfection