Oxidants and Ca+2 induce PGC-1alpha degradation through calpain.
Peroxisome proliferator activator receptor gamma coactivator 1alpha (PGC-1alpha) is a transcriptional coactivator known to mediate mitochondrial biogenesis. Whereas PGC-1alpha transcription is regulated by a variety of signaling cascades, the mechanisms of PGC-1alpha degradation have received less investigation. Thus, we investigated the mechanisms responsible for PGC-1alpha degradation in renal proximal tubular cells (RPTC). Amino acid sequence analysis of the PGC-1alpha protein revealed three PEST sequence-rich regions, predictive of proteolysis by calpains and/or the proteasome. Under basal conditions, treatment with the protein synthesis inhibitor cycloheximide resulted in rapid degradation of PGC-1alpha (t(1/2)=38 min), which was blocked by the proteasome inhibitor epoxomicin, but not the calpain inhibitor calpeptin. Oxidant exposure resulted in the degradation of both endogenous and adenovirally over-expressed PGC-1alpha, which was inhibited by calpeptin but not epoxomicin. Thapsigargin-induced release of ER Ca(2+) also stimulated calpain-dependent, epoxomicin-independent degradation of PGC-1alpha. Finally, Ca(2+) addition to lysates of RPTC over-expressing PGC-1alpha resulted in calpeptin-sensitive, epoxomicin-insensitive degradation of PGC-1alpha. In summary, we suggest two distinct mechanisms regulate PGC-1alpha: basal PGC-1alpha turnover by proteasome degradation and oxidant- and Ca(2+)-mediated PGC-1alpha degradation through calpain.
Rasbach
Kyle A
KA
Center for Cell Death, Injury, and Regeneration, Department of Pharmaceutical and Biomedical Sciences, South Carolina College of Pharmacy, Medical University of South Carolina, 280 Calhoun Street, PO Box 250140, SC 29425, USA.
Green
Peter T
PT
Schnellmann
Rick G
RG
D000595:Amino Acid Sequence; D000818:Animals; D002118:Calcium / Q000494:pharmacology; D002154:Calpain / Q000037:antagonists & inhibitors / Q000378:metabolism*; D002478:Cells, Cultured; D066298:In Vitro Techniques; D007687:Kidney Tubules, Proximal / Q000378:metabolism; D008928:Mitochondria / Q000378:metabolism; D008969:Molecular Sequence Data; D016877:Oxidants / Q000494:pharmacology; D047495:PPAR gamma / Q000378:metabolism*; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D011817:Rabbits; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D015534:Trans-Activators / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
D016877:Oxidants; D047495:PPAR gamma; D011994:Recombinant Proteins; D015534:Trans-Activators; D002154:Calpain; D046988:Proteasome Endopeptidase Complex; D002118:Calcium