Date of Award
Ongeri, Dr. Elimelda Moige
Meprins, metalloproteases that are highly expressed in the brush-border membranes of kidney proximal tubules, have been associated with ischemia-reperfusion induced kidney injury. Osteosarcoma 9 (OS9), a peripheral membrane protein, has been shown to selectively interact with the carboxyl-terminal tail of meprin beta (Î²). Additionally, OS9 was shown to promote oxygen-dependent degradation of the hypoxia-inducible factor 1Î± (HIF1Î±), a protein involved in oxygen homeostasis. However, it is not known if OS9 is a meprin substrate. The objective of this study was to determine if OS9 is a meprin substrate, and whether there is a correlation between expression of meprins, OS9, and HIF1Î± under hypoxic conditions. To determine if meprins are capable of degrading OS9, purified human OS9 was co incubated with activated recombinant forms of meprin A and B. Our results show that meprin B cleaves/degradation OS9. This was not observed for meprin A, suggesting isoform-specific cleavage. Mardin-Darby canine kidney (MDCK) cells and human embryonic kidney 293 cells transfected with meprin Î± or Î² cDNA were depleted of oxygen by exposure to 125 ÂµM cobalt chloride. Non-transfected cells served as controls. Western blot analysis was used to evaluate the nuclear fraction levels of OS9 and HIF1Î±. Our data showed that HIF-1Î± stabilized in the nucleus in a time-dependent manner and the levels of OS9 increased in non-transfected controls cells depleted of oxygen. To our knowledge, this is the first study to identify OS9 as a meprin B substrate. The degradation of OS9 by meprin B could impact the hypoxic response in kidney cells.
Martin, Barry L., "Meprin Interaction With Osteosarcoma 9 (Os9) And The Hypoxia Response Gene, Hypoxia Inducible Factor 1 (Hif1) Alpha, In Kidney Tubular Cells" (2013). Theses. 287.