Date of Award

2018

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Drug Discovery and Biomedical Sciences

College

College of Graduate Studies

First Advisor

Craig C. Beeson

Second Advisor

Rick G. Schnellmann

Third Advisor

Robin C. Muise-Helmericks

Fourth Advisor

James C. Chou

Fifth Advisor

Jill Turner

Abstract

Soluble Guanylyl Cyclase (sGC) is responsible for converting GTP to cyclic GMP (cGMP). sGC function and regulation is complex and cell -type dependent. An increase in cGMP production can target phosphodiesterases (PDEs), cGMP gated ion channels, and protein kinase G (PKG). Increasing sGC activity and inhibiting the degradation of cGMP by targeting PDEs are two approaches to maintaining cGMP levels in a given system. Interestingly, cGMP can also regulate mitochondrial biogenesis (MB), the generation of new and functional mitochondria. Previously in our laboratory, we have shown that MB is suppressed after ischemia and reperfusion (I/R) injury and certain mitochondrial biogenic compounds can accelerate recovery and attenuate the decrease in MB. In particular, we have shown that administration of an inhibitor of PDE5, sildenafil, can restore MB and renal function after I/R. However, the role of sGC in I/R is still under investigation. Here, we have elucidated a potential signaling pathway for the involvement of sGC in the suppression of MB. We performed I/R on mice and focused on the events that occur within the first 24 h of I/R injury. We optimized an sGC enzyme assay for the kidney to better understand the redox state of sGC. We proposed that the suppression of MB is cGMP-dependent and that PKG is a mediator of these effects. Moreover, we have proposed a role for ERK1/2 in the sGC/cGMP/PKG induced suppression of MB. Alternatively, we have shown that cGMP can induce MB in renal proximal tubule cells by 24 h with exposure to a cGMP analog, 8 -Br-cGMP. However, the mechanism behind this finding is unknown. Therefore, we treated renal proximal tubule cells with a 8 -Br- cGMP, for an 1 h to elucidate the mechanism behind this event. We measured the phosphorylation of serine and threonine residues on PGC-1α, the master regulator of MB, since phosphorylation can prolong the half -life of PGC-1α and induce MB. We found that the induction of MB is PKG dependent and that p38 MAPK plays a prominent role in the phosphorylation of PGC-1α. Here, we present sufficient evidence for the role of sGC signaling in regulating MB in the kidney.

Rights

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