Figure 4.

Regulatory mechanism governing mitochondrial biogenesis and mitochondrial homeostasis. Mitochondrial biosynthesis mainly occurs in the late stage of mitochondrial fission and mitophagy. PGC1α is the primary regulatory factor controlling mitochondrial biogenesis and is situated upstream of the mitochondrial biosynthesis reticular regulatory system. It is the hub connecting external signals to internal functional regulation within mitochondria. PGC1α promotes transcription of mitochondrial transcription factor A (TFAM) by activating nuclear respiratory factors 1 and 2 (Nrf-1 and Nrf-2) and regulates the citric acid and tricarboxylic acid cycles and, in turn, oxidative phosphorylation. In addition, ERP and PPAR-γ are members of the nuclear receptor transcription factor superfamily that act to regulate expression of target genes and the levels of TFAM transcription and mitochondrial biosynthesis.