Sperm capacitation is necessary for SNARE assembly in neurotoxin resistant complexes

PAVAROTTI M; MAYORGA LS

Buenos Aires

Congreso; Molecular mechanisms in cell signaling and gene expression. SAIB; 2013

sociedad Argentina de Investigación en Bioquímica y Biología Molecular

Capacitation is a not well defined process required for the acrosome reaction triggered by physiology stimuli. It can be achieved in vitro by incubation under specific conditions. The role of capacitation on the preparation of the membrane fusion mechanism responsible for acrosomal exocytosis is unknown. SNAREs proteins are fundamental proteins for membrane fusion inside cells. We have previous shown that neurotoxin sensitive SNARE proteins are necessary for acrosomal exocytosis. In capacitated resting sperm, SNAREs are assembled in neurotoxin resistant cis-complexes. The aim of this work was to study the dynamics of SNARE before and after sperm capacitation. For this purpose, we developed a membrane permeant neurotoxin by crosslinking a polyarginin peptide to recombinant Tetanus toxin light chain. SNAREs were insensible to the permeant neurotoxin in capacitated sperm. However, the toxin efficiently inhibited exocytosis when SNAREs complexes were disassembled upon stimulation. In contrast, SNAREs were sensible to the neurotoxin in not capacitated sperm indicating that SNAREs were not stabilized in cis complexes. Kinetic studies showed that two hours incubation under capacitating conditions were sufficient for SNAREs assembly in stable complexes. In brief, our results indicate that capacitation is important for the maturation of the fusion machinery responsible for acrosome reaction.