Coagulation proteases regulate renal ischemia-reperfusion-injury via the Y-box-binding protein-1

• Applicant: Professor Dr. Berend Isermann, since 9/2018
• Subject Area: Public Health, Healthcare Research, Social and Occupational Medicine
• Term: from 2015 to 2019
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 279290226

Ischemia-reperfusion injury (IRI) is the leading cause of acute renal failure. Although various candidate mechanisms regulating renal IRI have been identified in pre-clinical studies, trans-lational efforts have been disappointing. This necessitates the evaluation of new strategies and further research, including novel targets previously not linked with renal IRI. The cold shock protein YB-1 qualifies as a potential novel target in renal IRI, since (1) YB-1 is regulated in cardiac IRI and (2) a role of YB-1 in renal diseases other than IRI is established. YB-1 is a highly regulated protein involved in the regulation of inflammatory processes, including sterile inflammation in renal diseases such as IRI. Preliminary work conducted by our group demonstrates a function of YB-1 in renal IRI. Thus, protein levels of YB-1 are reduced in in vitro an in vivo IRI models and loss of YB-1 aggravates IRI induced changes in vitro and in vivo, establishing a role of YB-1 in renal IRI. The reduction of YB-1 protein levels is associated with increased ubiquitination of YB-1 and reduced expression of the deubiqui-tinating enzyme OTUB1 both in vitro and in vivo. However, the mechanism through which YB-1 is regulated, the intracellular signaling mechanism regulated by YB-1, and the modula-tion of extracellular YB-1 in renal IRI remain unknown. Interestingly, YB-1 is in part regulated by the coagulation protease thrombin (IIa), which modulates renal IRI. Previous work established that IIa induces partial proteolysis of YB-1 by the 20S-proteasome and nuclear translocation of the N-terminal YB-1 fragment in endothelial cells. The N-terminal fragment of YB-1 can bind to the Y-box or thrombin-response elements (TRE) of target genes (e.g. TGFbeta, tissue factor, protease activated receptors). As coagulation factors like IIa and activated protein C (aPC) are linked to renal IRI we speculate that YB-1 is regulated via protease dependent signalling in renal IRI. Indeed, preliminary work shows that aPC maintains protein levels of OTUB1 following IRI in vivo and in vitro. In addition aPC can reduce acetylation and secretion of YB-1 and, unlike IIa, inhibits the nuclear translocation of YB-1. In regard to YB-1 stability, aPC can maintain the YB-1 level after IRI in vitro, while IIa diminishes its level. The mechanisms through which coagulation proteases regulate the cold shock protein YB-1 in renal IRI remain unknown, and are subjects of this proposal. Thus, we intend to (1) identify the receptor complex required for aPC/IIa-dependent regulation of YB-1; (2) characterize the role of aPC/IIa-dependent ubiquitination for the regulation of YB-1; (3) determine the mechanistic relevance of aPC/IIa-dependent YB-1 regulation for the regulation of gene-expression; (4) determine whether aPC/IIa modifies proinflammatory signaling of extracellular YB-1. We expect that these studies will provide novel insights into the physiology and pathophysiology of renal IRI.

• DFG Programme: Research Grants
• Ehemaliger Antragsteller: Dr. Hongjie Wang, until 8/2018