The cysteine-rich domain of the secreted proprotein convertases PC5A and PACE4 functions as a cell surface anchor and interacts with tissue inhibitors of metalloproteinases.
The proprotein convertases PC5, PACE4 and furin contain a C-terminal cysteine-rich domain (CRD) of unknown function. We demonstrate that the CRD confers to PC5A and PACE4 properties to bind tissue inhibitors of metalloproteinases (TIMPs) and the cell surface. Confocal microscopy and biochemical analyses revealed that the CRD is essential for cell surface tethering of PC5A and PACE4 and that it colocalizes and coimmunoprecipitates with the full-length and C-terminal domain of TIMP-2. Surface-bound PC5A in TIMP-2 null fibroblasts was only observed upon coexpression with TIMP-2. In COS-1 cells, plasma membrane-associated PC5A can be displaced by heparin, suramin, or heparinases I and III and by competition with excess exogenous TIMP-2. Furthermore, PC5A and TIMP-2 are shown to be colocalized over the surface of enterocytes in the mouse duodenum and jejunum, as well as in liver sinusoids. In conclusion, the CRD of PC5A and PACE4 functions as a cell surface anchor favoring the processing of their cognate surface-anchored substrates, including endothelial lipase.
Nour
Nadia
N
Laboratory of Biochemical Neuroendocrinology, Clinical Research Institute of Montreal, Montreal, Quebec H2W 1R7, Canada.
Mayer
Gaétan
G
Mort
John S
JS
Salvas
Alexandre
A
Mbikay
Majambu
M
Morrison
Charlotte J
CJ
Overall
Christopher M
CM
Seidah
Nabil G
NG
D000818:Animals; D016466:CHO Cells; D019556:COS Cells; D002460:Cell Line; D002522:Chlorocebus aethiops; D006224:Cricetinae; D003412:Cricetulus; D003545:Cysteine; D006497:Heparan Sulfate / Q000502:physiology; D006801:Humans; D008565:Membrane Proteins / Q000378:metabolism / Q000502:physiology*; D045726:Metalloproteases / Q000378:metabolism; D051379:Mice; D045702:Proprotein Convertase 5 / Q000378:metabolism* / Q000502:physiology; D043484:Proprotein Convertases; D011499:Protein Processing, Post-Translational; D017434:Protein Structure, Tertiary / Q000502:physiology; D012697:Serine Endopeptidases / Q000378:metabolism* / Q000502:physiology; D019714:Tissue Inhibitor of Metalloproteinases / Q000378:metabolism*; D014162:Transfection
D003545:Cysteine; D006497:Heparan Sulfate; D008565:Membrane Proteins; D045726:Metalloproteases; D045702:Proprotein Convertase 5; D043484:Proprotein Convertases; D012697:Serine Endopeptidases; D019714:Tissue Inhibitor of Metalloproteinases; C442242:Timd2 protein, mouse; C080654:PCSK6 protein, human; C513086:Pcsk6 protein, mouse