Vesicular PtdIns(3,4,5)P3 and Rab7 are key effectors of sea urchin zygote nuclear membrane fusion

Newer Methods Drive Recent Insights into Rab GTPase Biology: An Overview

The conserved Ypt/Rab GTPases regulate all major intracellular protein traffic pathways, including secretion, endocytosis and autophagy. These GTPases undergo distinct changes in conformation between their GTP- and GDP-bound forms and cycle between the cytoplasm and membranes with the aid of their upstream regulators. When activated on the membrane in the GTP-bound form, they recruit their downstream effectors, which include components of vesicular transport. Progress in the past 5 years regarding mechanisms of Rab action, functions, and the effects of disruption of these functions on the well-being of cells and organisms has been propelled by advances in methodologies in molecular and cellular biology. Here, we highlight methods used recently to analyze regulation, localization, interactions, and function of Rab GTPases and their roles in human disease. We discuss contributions of these methods to new insights into Rabs, as well as their future use in addressing open questions in the field of Rab biology.

Hormesis of low-dose inhibition of pAkt1 (Ser473) followed by a great increase of proline-rich inositol polyphosphate 5-phosphatase (PIPP) level in oocytes

Hormesis describes a biphasic dose-response relationship generally characterized by a low-dose excitement and a high-dose inhibition. This phenomenon has been observed in the regulation of cell, organ, and organismic level. However, hormesis has not reported in oocytes. In this study, we observed, for the first time, hormetic responses of PIPP levels in oocytes by inhibitor of Akt1 or PKCδ. The expression of PIPP was detected by qPCR, immunofluorescent (IF), and Western Blot (WB). To observe the changes of PIPP levels, we used the inhibitors against pAkt1 (Ser473) or PKCδ, SH-6 or sotrastaurin with low and/or high-dose, treated GV oocytes and cultured for 4 h, respectively. The results showed that PIPP expression was significantly enhanced when oocytes were treated with SH-6 or sotrastaurin 10 μM, but decreased with SH-6 or sotrastaurin 100 μM. We also examined the changes of PIPP levels when GV oocytes were treated with exogenous PtdIns(3,4,5)P₃ or LY294002 for 4 h. Our results showed that PIPP level was enhanced much higher under the treatment of 0.1 μM PtdIns(3,4,5)P₃ than that of 1 μM PtdIns(3,4,5)P₃, which is consistent with the changes of PIPP when oocytes were treated with inhibitors of pAkt1 (Ser473) or PKCδ. In addition, with PIPP siRNA, we detected that down-regulated PIPP may affect distributions of Akt, Cdc25, and pCdc2 (Tyr15). Taken together, these results show that the relationships between PIPP and Akt may follow the principle of hormesis and play a key role during release of diplotene arrest in mouse oocytes.