The “acrosomal synapse” <subtitle>Subcellular organization by lipid rafts and scaffolding proteins exhibits high similarities in neurons and mammalian spermatozoa</subtitle>

Abstract

Mammalian spermatozoa are highly polarized cells composed of two morphological and functional compartments, each optimized for a special task. Although the compartmentalization into head and tail may as such represent the anatomical basis to avoid random diffusion of their special sets of signaling proteins and lipids, recent findings demonstrate the presence of lipid raft-derived membrane platforms and specific scaffolding proteins, thus indicating that additional smaller sub-domains exist in the two compartments of male germ cells. The aim of this review is to summarize new insights into the principles of sub-compartmentalization in mammalian spermatozoa. Special emphasis is placed on recent observations indicating that an “acrosomal synapse” is formed by lipid raft-derived membrane micro-environments and multidomain scaffolding proteins. Both mechanisms appear to be responsible for ensuring the attachment of the huge acrosomal vesicle to the overlaying plasma membrane, as well as for preventing an accidental spontaneous loss of the single acrosome.