PITPNC1 promotes the thermogenesis of brown adipose tissue under acute cold exposure

Brown adipose tissue (BAT) plays an essential role in non-shivering thermogenesis. The phosphatidylinositol transfer protein, cytoplasmic 1 (PITPNC1) is identified as a lipid transporter that reciprocally transfers phospholipids between intracellular membrane structures. However, the physiological significance of PITPNC1 and its regulatory mechanism remain unclear. Here, we demonstrate that PITPNC1 is a key player in thermogenesis of BAT. While Pitpnc1^(−/−) mice do not differ with wildtype mice in body weight and insulin sensitivity on either chow or high-fat diet, they develop hypothermia when subjected to acute cold exposure at 4℃. The Pitpnc1^(−/−) brown adipocytes exhibit defective β-oxidation and abnormal thermogenesis-related metabolism pathways in mitochondria. The deficiency of lipid mobilization in Pitpnc1^(−/−) brown adipocytes might be the result of excessive accumulation of phosphatidylcholine and a reduction of phosphatidic acid. Our findings have uncovered significant roles of PITPNC1 in mitochondrial phospholipid homeostasis and BAT thermogenesis.

Targeting histones for degradation in cancer cells as a novel strategy in cancer treatment

The anticancer therapies with the joint treatment of a histone deacetylase(HDAC) inhibitor and a DNA-damaging approach are actively under clinical investigations, but the underlying mechanism is unclear. Histone homeostasis is critical to genome stability, transcriptional accuracy, DNA repair process, senescence, and survival. We have previously demonstrated that the HDAC inhibitor, trichostatin A(TSA), could promote the degradation of the core histones induced by γ-radiation or the DNAalkylating agent methyl methanesulfonate(MMS) in non-cancer cells, including mouse spermatocyte and embryonic fibroblast cell lines. In this study, we found that the joint treatment by TSA and MMS induced the death of the cultured cancer cells with an additive effect, but induced degradation of the core histones synergistically in these cells. We then analyzed various combinations of other HDAC inhibitors, including suberoylanilide hydroxamic acid and valproate sodium, with MMS or other DNAdamaging agents, including etoposide and camptothecin. Most of these combined treatments induced cell death additively, but all the tested combinations induced degradation of the core histones synergistically. Meanwhile, we showed that cell cycle arrest might not be a primary consequence for the joint treatment of TSA and MMS. Given that clinic treatments of cancers jointly with an HDAC inhibitor and a DNA-damaging approach often show synergistic effects, histone degradation might more accurately underlie the synergistic effects of these joint treatments in clinic applications than other parameters, such as cell death and cell cycle arrest. Thus, our studies might suggest that the degradation of the core histones can serve as a new target for the development of cancer therapies.