title: In vitro regulatory effect of epididymal serpin CRES on protease activity of proprotein convertase PC4/PCSK4.
abstract: PC4 or PCSK4 belongs to the 9-member superfamily of mammalian subtilases collectively called Proprotein Convertases or Proprotein Convertase Subtilisin/Kexins that convert inactive precursor proteins into their active mature forms by endoproteolytic cleavage. PC4-activity plays a crucial role in mammalian fertilization via activation of sperm surface proteins. PC4 knockout mice exhibit severely impaired male fertility due to premature sperm acrosome reaction. Regulation of sperm-PC4 activity during its storage and transport through epididymis is an important determinant for ultimate egg-binding and fertilizing capacities of sperms. Herein we show that epididymal serpin CRES (cystatin related epididymal spermatogenic) recombinant protein inhibits PC4 activity in vitro in a differential manner when measured against the fluorogenic substrate Boc- RVRR-MCA depending on its oligomeric state. Thus while CRES-dimer exhibits K(i) ∼8 μM, the corresponding monomer showed K(i) > 100 μM. Both forms also blocked PC4-mediated processing of human proIGF-2 in human placenta tropoblast cell line with dimer being more efficient. Using specific inhibitors and substrates, we also demonstrated the presence of PC4-like activity and CRES protein in varying levels in the fluids of various epididymal compartments. Our observations suggest a potential function of CRES as a regulator of PC4 in sperm-egg interaction and fertilization.
authors: Laboratories of Chronic Disease Program, Ottawa Hospital Research Institute, UOttawa, Ottawa, ON K1Y 4E9, Canada.
authors: P
authors: P
authors: Mishra
authors: Q
authors: Q
authors: Qiu
authors: A
authors: A
authors: Gruslin
authors: Y
authors: Y
authors: Hidaka
authors: M
authors: M
authors: Mbikay
authors: A
authors: A
authors: Basak
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001667:Binding, Competitive; D002460:Cell Line; D002851:Chromatography, High Pressure Liquid; D015891:Cystatins / Q000096:biosynthesis / Q000737:chemistry* / Q000302:isolation & purification; D004822:Epididymis / Q000201:enzymology*; D006801:Humans; D008297:Male; D051379:Mice; D008969:Molecular Sequence Data; D043484:Proprotein Convertases; D011485:Protein Binding; D055503:Protein Multimerization; D020836:Protein Structure, Quaternary; D059748:Proteolysis; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000737:chemistry / Q000302:isolation & purification; D012697:Serine Endopeptidases / Q000096:biosynthesis / Q000737:chemistry* / Q000302:isolation & purification; D015842:Serine Proteinase Inhibitors / Q000096:biosynthesis / Q000737:chemistry* / Q000302:isolation & purification; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D013381:Subtilisins
chemical_list: D015891:Cystatins; D011994:Recombinant Proteins; D015842:Serine Proteinase Inhibitors; C078310:Cst8 protein, mouse; C489717:Pcsk4 protein, mouse; D043484:Proprotein Convertases; D012697:Serine Endopeptidases; D013381:Subtilisins