日本东北大学研究人员最新报告说，他们在动物实验中发明了利用诱导多能干细胞制成釉细胞的技术，成釉细胞可以发育出牙齿最坚硬部分——牙釉质。
日本东北大学教授福本敏等人报告说，他们利用来自实验鼠胚胎的牙源性上皮细胞和京都大学教授山中伸弥培育的诱导多能干细胞进行培养，发现约95%的诱导多能干细胞分化成了成釉细胞。经过确认，这些细胞中含有作为牙釉质成分的成釉蛋白。
牙釉质又名珐琅质，是牙冠表层的白色、坚硬、透明组织，保护着牙齿内部的牙本质和牙髓组织。“制造”牙釉质的成釉细胞在一定年龄后就无法生成，所以牙釉质遭破坏后无法再生，碳酸饮料对牙釉质的腐蚀性较强，及时以正确方式刷牙漱口对保护牙釉质至关重要。
这一成果已发表在《生物化学杂志》网络版上。
Phospholipase C-related, but catalytically inactive protein PRIP modulates SNAP-25 phosphorylation and exocytosis
Jing Gao, Hiroshi Takeuchi, Zhao Zhang, Mitsunori Fukuda and Masato Hirata
Exocytosis is one of the most fundamental cellular events. The basic mechanism of the final step, membrane fusion, is mediated by the formation of the SNARE complex, which is modulated by the phosphorylation of proteins controlled by the concerted actions of protein kinases and phosphatases. We have previously shown that a protein phosphatase-1 (PP1) anchoring protein, PRIP (phospholipase C-related, but catalytically inactive protein), has an inhibitory role in regulated exocytosis. The current study investigated the involvement of PRIP in the phospho-dependent modulation of exocytosis. Dephosphorylation of SNAP-25 (synaptosome-associated protein of 25kDa) was mainly catalyzed by PP1 and the process was modulated by wild-type PRIP, but not by the mutant (F97A) lacking PP1-binding ability in in vitro studies. We then examined the role of PRIP in phospho-dependent regulation of exocytosis in cell-based studies using a pheochromocytoma cell line, PC12 cells, that secrete noradrenalin. Exogenous expression of PRIP accelerated the dephosphorylation process of phosphorylated SNAP-25 after forskolin or phorbol ester treatment of the cells. The phospho-states of SNAP-25 were correlated with noradrenalin secretion, which was enhanced by forskolin or phorbol ester treatment and modulated by PRIP expression in PC12 cells. Both SNAP-25 and PP1 were co-precipitated in anti-PRIP immunocomplex isolated from PC12 cells expressing PRIP. Collectively, together with our previous observation regarding the roles of PRIP in PP1 regulation, these results suggest that PRIP is involved in the regulation of the phospho-states of SNAP-25 by modulating the activity of PP1, thus regulating exocytosis.
