INVESTIGADORES
MAYORGA Luis Segundo
artículos
Título:
ADP Ribosylation Factor 6 (ARF6) Promotes Acrosomal Exocytosis by Modulating Lipid Turnover and Rab3A Activation.
Autor/es:
PELLETAN, LE; SUHAIMAN, L; VAQUER, CC; BUSTOS MA; DE BLAS GA; VITALE N; MAYORGA LS; BELMONTE SA
Revista:
JOURNAL OF BIOLOGICAL CHEMISTRY
Editorial:
AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC
Referencias:
Lugar: Bethesda, Maryland; Año: 2015 vol. 290 p. 9823 - 9841
ISSN:
0021-9258
Resumen:
Regulated secretion is a central issue for the specific function of many cells; for instance, mammalian sperm acrosomal exocytosis is essential for egg fertilization. ARF6 (ADPribosylation factor 6) is a small GTPase implicated in exocytosis but its downstream effectors remain elusive. We combined biochemical, functional and microscopy-based methods to show that ARF6 is present in human sperm, localizes to the acrosomal region, and is required for calcium and diacylglycerol (DAG)-induced exocytosis. Results from pull-down assays show that ARF6 exchanges GDP for GTP in sperm challenged with different exocytic stimuli. Myristoylated and GTPS-loaded ARF6 (active form) induces sperm exocytosis even in the absence of extracellular calcium. We demonstrated that ARF6 stimulates a sperm PLD activity, to produce phosphatidic acid, and boosts the synthesis of phosphatidylinositol 4,5- bisphosphate (PIP2). Although both lipids are required for exocytosis they do not induce secretion by themselves. In this report, we unveiled the ARF6 signaling that promotes regulated secretion. We present, direct evidence demonstrating that active ARF6 increases PLC activity, causing PIP2 hydrolysis, and IP3- dependent intraacrosomal calcium release. For the first time, we identified a link between ARF6 and PLC signaling. Moreover, active ARF6 increases the exchange of GDP for GTP on Rab3A, a prerequisite for secretion. Further, we found that ARF6 triggers a mechanism involving novel targets. We propose that exocytic stimuli activate ARF6, which induces acrosomal calcium efflux and assembles the fusion machinery leading to membrane fusion. This report highlights the physiological importance of ARF6 as a key molecule for human sperm exocytosis and fertilization.