IDENTIFICATION OF A PLASMA MEMBRANE FUSION SUPERFAMILY, FUSEXIN, SUFFICIENT TO FUSE GAMETES, ENVELOPE

VALANSI, CLARI; MOI, DAVID; MATVEEV, ELENA; GRAÑA, MARTIN; ROMERO, HECTOR; AGUILAR, P.S.; PODBILEWICZ, BENJAMIN

CORDOBA

Congreso; 52th Annual Meeting Argentine Society for Biochemistry and Molecular Biology; 2016

SAIB

Gamete fusion enables sexual reproduction. While proteins mediating cell-cell fusion in tissues have been identified (e.g. C. elegans EFF-1), the machinery catalyzing sperm-egg fusion is still unknown. HAP2 proteins are candidate fertilization fusogens as their inactivation results in sterility due to failure in gamete fusion in a number of organisms. To determine whether HAP2 is not only necessary for fertilization but is also sufficient for cell-cell fusion we express Arabidopsis HAP2 in cells that normally do not fuse. Heterologous expression in Baby Hamster Kidney cells results in cell-cell fusion, with HAP2 presence required in both fusing cells. This bilateral action can be recapitulated replacing the plant gene with EFF-1 in one of the fusing cells, indicating that HAP2 and EFF-1 can interact and share a similar fusion mechanism. Modeling of HAP2 predicts it is homologous to C. elegans EFF-1 somatic fusogen and class II fusion proteins from enveloped viruses (e.g. dengue and Zika viruses). Based on functional and structural conservation of these sexual, viral and somatic cell fusion proteins we name them FUSEXINS: FUSion proteins for sexual reproduction and EXoplasmic merger of plasma membranes. We propose that Fusexins derive from a common ancestor linking the origins and evolution of sexual reproduction, enveloped viruses invasion and somatic cell fusion.