CCN6 regulates mitochondrial respiratory complex assembly and activity

Abstract

Cellular communication network factor 6 (CCN6) mutations are linked with Progressive Pseudo Rheumatoid Dysplasia (PPRD) a debilitating musculoskeletal disorder. The function of CCN6 and the mechanism of PPRD pathogenesis remain unclear. Accordingly, we focused on the functional characterization of CCN6 and CCN6 mutants. Using size exclusion chromatography and native polyacrylamide gel electrophoresis we demonstrated that CCN6 is present as a component of the mitochondrial respiratory complex in human chondrocyte lines. By means of siRNA‐mediated transfection and electron microscopy we showed that moderate reduction in CCN6 expression decreases the RER– mitochondria inter‐membrane distance. Parallel native PAGE, immunoblotting and Complex I activity assays furthermore revealed increase in both mitochondrial distribution of CCN6 and mitochondrial respiratory complex assembly/activity in CCN6 depleted cells. CCN6 mutants resembling those linked with PPRD, which were generated by CRISPR‐Cas9 technology displayed low level of expression of mutant CCN6 protein and inhibited respiratory complex assembly/activity. Electron microscopy and MTT assay of the mutants revealed abnormal mitochondria and poor cell viability. Taken together, our results indicate that CCN6 regulates mitochondrial respiratory complex assembly/activity as part of the mitochondrial respiratory complex by controlling the proximity of RER with the mitochondria, and CCN6 mutations disrupt mitochondrial respiratory complex assembly/activity resulting in mitochondrial defects and poor cell viability.

CCN6improves hepatic steatosis, inflammation, and fibrosis in non‐alcoholic steatohepatitis

“…30 CCN6 maintains the structure and function of mitochondria and regulates ROS production. 9,10 As such, our findings provide an important pavement in the search for the mechanisms by which CCN6 plays a role in NASH.…”

“…Increased accumulation of FFA in hepatocytes leads to enhanced mitochondrial β‐oxidation and increased production of ROS, 29 whilst endogenous antioxidant systems become less efficient in the steatotic liver 30 . CCN6 maintains the structure and function of mitochondria and regulates ROS production 9,10 . As such, our findings provide an important pavement in the search for the mechanisms by which CCN6 plays a role in NASH.…”

“…Functional studies have demonstrated that CCN6 regulates cellular ROS production, which is closely related to mitochondrial oxidative stress. [8][9][10][11] Meanwhile, CCN6 has been shown to be associated with tumorigenesis in various tissue. [12][13][14][15] However, the function of CCN6 in the pathogenesis of NAFLD/NASH remains to be identified.…”

Progressive Pseudorheumatoid Dysplasia of Childhood (PPRD)—A Case Series with Recurrent c.740_741del Variant

“…14 However, recent functional studies demonstrated a role of CCN6 in the mitochondrial respiratory complex assembly/activity and ATP production. 15 Hence, mutations in CCN6 result in mitochondrial defects and deprived cell survival. Sengupta et al 16 used a zebrafish model to study functional effects of CCN6 protein.…”

CCN6 influences transcription and controls mitochondrial mass and muscle organization

“…Gel filtration chromatography of total nuclear lysate was performed following previously documented procedures 31,33 . The total nuclear lysate was prepared from cultured C28/I2 cells following the protocol described before.…”