Cell–cell fusogens are glycoproteins that facilitate the fusion of cell to cell membranes. Cell–cell fusion is critical for the merging of gamete genomes and development of organs in multicellular organisms. The engagement of fusogenic proteins across cell membranes are driven by actin-propelled membrane protrusions.
EFF-AFF are the identifiers of type 1 glycoproteins that make up cell–cell fusogens. They were first identified when EFF1 mutants were found to block cell fusion in all epidermal and vulval epithelia in the roundworm, Caenorhabditis elegans. EFF-AFF is a family of type I membrane glycoproteins that act as cell–cell fusogens, named from 'Anchor cell fusion failure'. However, fusion between the anchor-cell and the (uterine seam) utse syncytium that establishes a continuous uterine-vulval tube proceeds normally in eff-1 mutants and thus Aff1 was established as necessary for this and the fusion of heterologous cells in C. elegans. The transmembrane forms of these proteins, like most viral fusogens, possess an N-terminal signal sequence followed by a long extracellular portion, a predicted transmembrane domain, and a short intracellular tail. A striking conservation in the position and number of all 16 cysteines in the extracellular portion of EFF-AFF proteins from different nematode species suggests that these proteins are folded in a similar 3D structure that is essential for their fusogenic activity. C. elegans AFF-1 and EFF-1 proteins are essential for developmental cell-to-cell fusion and can merge insect cells. Thus FFs comprise an ancient family of cellular fusogens that can promote fusion when expressed on a viral particle.
- Cell membrane
- Cellular differentiation
- Fusion mechanism
- Interbilayer forces in membrane fusion
- Lipid bilayer fusion
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