Yeast filamentation signaling is connected to a specific substrate translocation mechanism of the Mep2 transceptor

by Ana Sofia Brito, Benjamin Neuh äuser, René Wintjens, Anna Maria Marini, Mélanie Boeckstaens The dimorphic transition from the yeast to the filamentous form of growth allows cells to explore their environment for more suitable niches and is often crucial for the virulence of pathogenic fungi. In contrast to their Mep1/3 paralogues, fungal Mep2-type ammonium transport proteins of the conse rved Mep-Amt-Rh family have been assigned an additional receptor role required to trigger the filamentation signal in response to ammonium scarcity. Here, genetic, kinetic and structure-function analyses were used to shed light on the poorly characterized signaling role ofSaccharomyces cerevisiae Mep2. We show that Mep2 variants lacking the C-terminal tail conserve the ability to induce filamentation, revealing that signaling can proceed in the absence of exclusive binding of putative partner to the largest cytosolic domain of the protein. Our data support that filamentation signaling requires the conformational changes accompanying substrate translocation through the pore crossing the hydrophobic core of Mep2. pHluorin reporter assays show that the transport activity of Mep2 and of non-signaling Mep1 differently affect yeast cytosolic pHin vivo, and that the unique pore variant Mep2H194E, with apparent uncoupling of transport and signaling functions, acquires increased ability of acidification. Functional characterization inXenopus oocytes reveals that Mep2 mediates electroneutral sub...
Source: PLoS Genetics - Category: Genetics & Stem Cells Authors: Source Type: research