The “acrosomal synapse”

Abstract

Mammalian spermatozoa are highly polarized cells composed of two morphological and functional units, each optimized for a special task. Although the apparent division 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 smaller sub-domains exist in the two functional units of male germ cells. The aim of this review is to summarize new insights into the principles of subcellular organization 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.

NAADP and the two-pore channel protein 1 participate in the acrosome reaction in mammalian spermatozoa

“…Moreover, colocalization of IP 3 -R and TPC1 in detergent-resistant lipid raft platforms (Supplemental Figure S6) was observed. These lipid rafts embody a membrane-organizing principle of spatial sequestration, which leads to a subcellular concentration of components of the secretory machinery at the “acrosomal synapse” ( Zitranski et al. , 2010 ), the posterior region of the sperm head ( Gadella et al.…”

“…, 2010 ), the posterior region of the sperm head ( Gadella et al. , 2008 ; Nixon and Aitken, 2009 ; Zitranski et al. , 2010 ).…”

The Role of Taste Receptor mTAS1R3 in Chemical Communication of Gametes

“…The authors [33] demonstrated a presence of N-methyl-D-aspartate (NMDA) glutamate receptor NR2B and sodium-dependent glutamate transporter GLT1 in mouse and human sperm and showed that mouse sperm possessed the glutamate uptake property in similar way as brain did. Due to the fact that the acrosome vesicle exocytosis displays similar physiology with the active zone of the presynaptic terminal in neurons where neurotransmitter vesicle fusion occurs, and thus may be termed "acrosomal synapse" [34], the research from the field of neuroscience is relevant to sperm reproductive physiology.…”

Ultrastructure and lipid composition of detergent-resistant membranes derived from mammalian sperm and two types of epithelial cells

“…Both the DRM of sperm as well as this apical sperm head surface are rafts that aggregate and are extremely highly enriched in zona pellucida and/or cumulus binding protein complexes (van Gestel et al 2005a ; 2007 ; Nixon and Aitken 2009 ; Nixon et al 2009 ; 2011 ; Reid et al 2011 ; Bromfield and Nixon 2013 a, 2013b ; Caballero et al 2012 ; Jones et al 2010 ; Tanphaichitr et al 2007 ). The same surface area contains SNARE proteins (Tsai et al 2007 ), which are involved in the docking of the acrosome during sperm capacitation (Ackermann et al 2008 ; Tsai et al 2010 , 2012 ; Zitranski et al 2010 ). Interestingly, the association of CDC42 and the oligomerization of caveolin-1 have been described (Baltiérrez-Hoyos et al 2012 ) and also, the involvement of CDC42 in lipid raft-mediated synaptic delivery has recently been reported (Brachet et al 2015 ).…”