Molecular Characterization of Peroxisome Proliferator-Activated Receptor-Gamma Coactivator-1α (PGC1α) and Its Role in Mitochondrial Biogenesis in Blunt Snout Bream (Megalobrama amblycephala).

Xiaojun Song,Wenhao Zhou,Kangle Lu,Samad Rahimnejad,Linsen Cai

doi:10.3389/fphys.2018.01957

Xiaojun Song, Wenhao Zhou + Show 3 more

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https://doi.org/10.3389/fphys.2018.01957

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Abstract

PGC1α is a transcriptional coactivator that plays key roles in mitochondrial biogenesis, so exploring its molecular characterization contributes to the understanding of mitochondrial function in cultured fish. In the present study, a full-length cDNA coding PGC1α was cloned from the liver of blunt snout bream (Megalobrama amblycephala) which covered 3741 bp with an open reading frame of 2646 bp encoding 881 amino acids. Sequence alignment and phylogenetic analysis revealed high conservation with other fish species, as well as other higher vertebrates. Comparison of the derived amino acid sequences indicates that, as with other fish, there is a proline at position 176 (RIRP) compared to a Thr in the mammalian sequences (RIRT). To investigate PGC1α function, three in vitro tests were carried out using primary hepatocytes of blunt snout bream. The effect of AMPK activity on the expression of PGC1α was determined by the culture of the hepatocytes with an activator (Metformin) or inhibitor (Compound C) of AMPK. Neither AMPK activation nor inhibition altered PGC1α expression. Knockdown of PGC1α expression in hepatocytes using small interfering RNA (si-RNA) was used to determine the role of PGC1α in mitochondrial biogenesis. No significant differences in the expression of NRF1 and TFAM, and mtDNA copy number were found between control and si-RNA groups. Also, hepatocytes were cultured with oleic acid, and the findings showed the significant reduction of mtDNA copy number in oleic acid group compared to control. Moreover, oleic acid down-regulated the expression of NRF1 and TFAM genes, while PGC1α expression remained unchanged. Our findings support the proposal that PGC1α may not play a role in mitochondrial biogenesis in blunt snout bream hepatocytes.

Highlights

MATERIALS AND METHODSThe peroxisome proliferator-activated receptor-gamma coactivator 1 (PGC1) family members are transcriptional coactivators that play key roles in the transcriptional control of mitochondrial biogenesis and respiratory function (Scarpulla, 2011)
The AMPK-PGC1α-nuclear respiratory factor 1 (NRF1) pathway is well established in mammalian models, but this axis remains unclear in fish
The full-length PGC1α cDNA sequence was submitted to Genbank

Summary

Introduction

MATERIALS AND METHODSThe peroxisome proliferator-activated receptor-gamma coactivator 1 (PGC1) family members are transcriptional coactivators that play key roles in the transcriptional control of mitochondrial biogenesis and respiratory function (Scarpulla, 2011). The other family members including PGC1β and PGC1-related coactivator (PRC) were subsequently discovered through database searches for PGC1α homologs. These three PGC1 proteins share some features but they have distinct functions. The role of PGC1α in mitochondrial biogenesis of mammals and birds has been well established, it still remains to be elucidated in fish (Bremer et al, 2016). The findings of a recent study indicated that the AMPK-PGC1α-NRF1 may be disrupted in fish (Bremer et al, 2016) This may indicate that different species probably adopt distinct solutions for controlling mitochondrial biogenesis. From an evolutionary point of view, duplication events and mutations often induce divergence/diversity in function of genes between fish and mammals (Sémon and Wolfe, 2007)

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