[Study of senescence protein p66Shc on myocardial tissue repair in adult mice].

Our previous study has shown that p66Shc plays an important role in the process of myocardial regeneration in newborn mice, and p66Shc deficiency leads to weakened myocardial regeneration in newborn mice. This study aims to explore the role of p66Shc protein in myocardial injury repair after myocardial infarction in adult mice, in order to provide a new target for the treatment of myocardial injury after myocardial infarction. Mouse myocardial infarction models of adult wild-type (WT) and p66Shc knockout (KO) were constructed by anterior descending branch ligation. The survival rate and heart-to-body weight ratio of two models were compared and analyzed. Masson's staining was used to identify scar area of injured myocardial tissue, and myocyte area was determined by wheat germ agglutinin (WGA) staining. TUNEL staining was used to detect the cardiomyocyte apoptosis. The protein expression of brain natriuretic peptide (BNP), a common marker of myocardial hypertrophy, was detected by Western blotting. The results showed that there was no significant difference in survival rate, myocardial scar area, myocyte apoptosis, and heart weight to body weight ratio between the WT and p66ShcKO mice after myocardial infarction surgery. Whereas the protein expression level of BNP in the p66ShcKO mice was significantly down-regulated compared with that in the WT mice. These results suggest that, unlike in neonatal mice, the deletion of p66Shc has no significant effect on myocardial injury repair after myocardial infarction in adult mice.

Structural insights into the mechanism of human NPC1L1-mediated cholesterol uptake.

Niemann-Pick C1-like 1 (NPC1L1) protein plays a central role in the intestinal cholesterol absorption and is the target of a drug, ezetimibe, which inhibits NPC1L1 to reduce cholesterol absorption. Here, we present cryo-electron microscopy structures of human NPC1L1 in apo state, cholesterol-enriched state, and ezetimibe-bound state to reveal molecular details of NPC1L1-mediated cholesterol uptake and ezetimibe inhibition. Comparison of these structures reveals that the sterol-sensing domain (SSD) could respond to the cholesterol level alteration by binding different number of cholesterol molecules. Upon increasing cholesterol level, SSD binds more cholesterol molecules, which, in turn, triggers the formation of a stable structural cluster in SSD, while binding of ezetimibe causes the deformation of the SSD and destroys the structural cluster, leading to the inhibition of NPC1L1 function. These results provide insights into mechanisms of NPC1L1 function and ezetimibe action and are of great significance for the development of new cholesterol absorption inhibitors.

The acidic ribosomal protein P2 from Euplotes octocarinatus is phosphorylated at its N-terminal domain.

The eukaryotic acid ribosomal P0, P1, and P2 proteins share a conserved flexible C-terminal tail that is rich in acidic residues, which are involved in the interaction with elongation factor 2 during protein synthesis. Our previous work suggested that the acidic ribosomal P proteins from Euplotes octocarinatus have a special C-terminal domain. To further understand this characteristic feature, both P2 and elongation factor 2 from E. octocarinatus were overexpressed, for the first time, in Escherichia coli in this study. GST pull-down assay indicated that P2 protein from E. octocarinatus (EoP2) interacted specifically with the N-terminal domain of elongation factor 2 from E. octocarinatus (EoEF-2) in vitro. The interacting part of EoP2 is in the C-terminal domains, consistent with the observation in other organisms. Phosphorylation of the recombinant EoP2 was performed in vitro using multiple methods such as (31)P-NMR spectroscopy, native PAGE, and Phos-tag(TM) SDS-PAGE. Results showed that ribosomal protein EoP2 was phosphorylated by casein kinase II at serine 21 located at the N terminus. This phosphorylation site identified in EoP2 is quite different from that of P2 from other organisms, in which the phosphorylation site is located in the conserved C-terminal region.