Hypoxia Associated Proteolytic Processing of OS-9 by the Metalloproteinase Meprinβ

Abstract

Meprin metalloproteases play a role in the pathology of ischemia/reperfusion- (IR-) induced renal injury. The endoplasmic reticulum-associated protein, osteosarcoma-9 (OS-9), has been shown to interact with the carboxyl-terminal tail of meprinβ. More importantly, OS-9 interacts with the hypoxia inducible factor-1α(HIF-1α) and the prolyl-hydroxylase, proteins which mediate the cell’s response to hypoxia. To determine if OS-9 is a meprin substrate, kidney proteins from meprinαβknockout mice (αβKO) (which lack endogenous meprins) and purified human OS-9 were incubated with activated forms of meprin A and meprin B, and Western blot analysis was used to evaluate proteolytic processing of OS-9. Fragmentation of OS-9 was observed in reactions with meprin B, but not meprin A. To determine whether meprin B cleaves OS-9in vivo, wild-type (WT) and meprinαβKO mice were subjected to IR-induced renal injury. Fragmentation of OS-9 was observed in kidney proteins from WT mice subjected to IR, but not in meprinαβKO counterparts. Transfection of kidney cells (MDCK and HEK293) with meprinβcDNA prevented accumulation of OS-9 following exposure to the hypoxia mimic, CoCl2. These data suggest that meprinβinteraction with OS-9 plays a role in the hypoxia response associated with IR-induced renal injury.