Blockage of TMEM189 induces G2/M arrest and inhibits the growth of breast tumors.

Cancer is the major cause of premature death in humans worldwide, demanding more efficient therapeutics. Aberrant cell proliferation resulting from the loss of cell cycle regulation is the major hallmark of cancer, so targeting cell cycle is a promising strategy to combat cancer. However, the molecular mechanism underlying the dysregulation of cell cycle of cancer cells remains poorly understood. TMEM189, a newly identified protein, plays roles in the biosynthesis of ethanolamine plasmalogen and the regulation of autophagy. Here, we demonstrated that the expression level of TMEM189 was negatively correlated with the survival rate of the cancer patients. TMEM189 deficiency significantly suppresses the cancer cell proliferation and migration, and causes cell cycle G2/M arrest both in vitro and in vivo. Furthermore, TMEM189 depletion suppressed the growth of breast tumors in vivo. Taken together, our work indicated that TMEM189 promotes cancer progression by regulating cell cycle G2/M transition, suggesting that it is a promising target in cancer therapy.

Fatty liver disease protective MTARC1 p.A165T variant reduces the protein stability of MTARC1.

Non-alcoholic fatty liver disease (NAFLD) is one of the most common causes of liver disease worldwide. MTARC1, encoded by the MTARC1 gene, is a mitochondrial outer membrane-anchored enzyme. Interestingly, the MTARC1 p.A165T (rs2642438) variant is associated with a decreased risk of NAFLD, indicating that MTARC1 might be an effective target. It has been reported that the rs2642438 variant does not have altered enzymatic activity so we reasoned that this variation may affect MTARC1 stability. In this study, MTARC1 mutants were generated and stability was assessed using a protein stability reporter system both in vitro and in vivo. We found that the MTARC1 p.A165T variant has dramatically reduced the stability of MTARC1, as assessed in several cell lines. In mice, the MTARC1 A168T mutant, the equivalent of human MTARC1 A165T, had diminished stability in mouse liver. Additionally, several MTARC1 A165 mutants, including A165S, A165 N, A165V, A165G, and A165D, had dramatically decreased stability as well, suggesting that the alanine residue of MTARC1 165 site is essential for MTARC1 protein stability. Collectively, our data indicates that the MTARC1 p.A165T variant (rs2642438) leads to reduced stability of MTARC1. Given that carriers of rs2642438 show a decreased risk of NAFLD, the findings herein support the notion that MTARC1 inhibition may be a therapeutic target to combat NAFLD.