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How pig sperm prepares to fertilize: stable acrosome docking to the plasma membrane.

ABSTRACT: BACKGROUND: Mammalian sperms are activated in the oviduct. This process, which involves extensive sperm surface remodelling, is required for fertilization and can be mimicked under in vitro fertilization conditions (IVF). METHODOLOGY/PRINCIPAL FINDINGS: Here we demonstrate that such treatments caused stable docking and priming of the acrosome membrane to the apical sperm head surface without the emergence of exocytotic membrane fusion. The interacting membranes could be isolated as bilamellar membrane structures after cell disruption. These membrane structures as well as whole capacitated sperm contained stable ternary trans-SNARE complexes that were composed of VAMP 3 and syntaxin 1B from the plasma membrane and SNAP 23 from the acrosomal membrane. This trans-SNARE complex was not observed in control sperm. CONCLUSIONS/SIGNIFICANCE: We propose that this capacitation driven membrane docking and stability thereof is a preparative step prior to the multipoint membrane fusions characteristic for the acrosome reaction induced by sperm-zona binding. Thus, sperm can be considered a valuable model for studying exocytosis.

SUBMITTER: Tsai PS

PROVIDER: S-EPMC2887851 | biostudies-literature | 2010

REPOSITORIES: biostudies-literature

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How pig sperm prepares to fertilize: stable acrosome docking to the plasma membrane.

Tsai Pei-Shiue PS Garcia-Gil Núria N van Haeften Theo T Gadella Bart M BM

PloS one 20100618 6

<h4>Background</h4>Mammalian sperms are activated in the oviduct. This process, which involves extensive sperm surface remodelling, is required for fertilization and can be mimicked under in vitro fertilization conditions (IVF).<h4>Methodology/principal findings</h4>Here we demonstrate that such treatments caused stable docking and priming of the acrosome membrane to the apical sperm head surface without the emergence of exocytotic membrane fusion. The interacting membranes could be isolated as ...[more]

PMID: 20585455

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Project description:?-SNAP has an essential role in membrane fusion that consists of bridging cis SNARE complexes to NSF. ?-SNAP stimulates NSF, which releases itself, ?-SNAP, and individual SNAREs that subsequently re-engage in the trans arrays indispensable for fusion. ?-SNAP also binds monomeric syntaxin and NSF disengages the ?-SNAP/syntaxin dimer. Here, we examine why recombinant ?-SNAP blocks secretion in permeabilized human sperm despite the fact that the endogenous protein is essential for membrane fusion. The only mammalian organism with a genetically modified ?-SNAP is the hyh mouse strain, which bears a M105I point mutation; males are subfertile due to defective sperm exocytosis. We report here that recombinant ?-SNAP-M105I has greater affinity for the cytosolic portion of immunoprecipitated syntaxin than the wild type protein and in consequence NSF is less efficient in releasing the mutant. ?-SNAP-M105I is a more potent sperm exocytosis blocker than the wild type and requires higher concentrations of NSF to rescue its effect. Unlike other fusion scenarios where SNAREs are subjected to an assembly/disassembly cycle, the fusion machinery in sperm is tuned so that SNAREs progress uni-directionally from a cis configuration in resting cells to monomeric and subsequently trans arrays in cells challenged with exocytosis inducers. By means of functional and indirect immunofluorescense assays, we show that recombinant ?-SNAPs--wild type and M105I--inhibit exocytosis because they bind monomeric syntaxin and prevent this SNARE from assembling with its cognates in trans. Sequestration of free syntaxin impedes docking of the acrosome to the plasma membrane assessed by transmission electron microscopy. The N-terminal deletion mutant ?-SNAP-(160-295), unable to bind syntaxin, affects neither docking nor secretion. The implications of this study are twofold: our findings explain the fertility defect of hyh mice and indicate that assembly of SNAREs in trans complexes is essential for docking.

Dataset Information

How pig sperm prepares to fertilize: stable acrosome docking to the plasma membrane.

Publications

How pig sperm prepares to fertilize: stable acrosome docking to the plasma membrane.

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