MID1, a novel Saccharomyces cerevisiae gene encoding a plasma membrane protein, is required for Ca2+ influx and mating.

Abstract

By establishing a unique screening method, we have isolated yeast mutants that die only after differentiating into cells with a mating projection, and some of them are also defective in Ca2+ signaling. The mutants were classified into five complementation groups, one of which we studied extensively. This mutation defines a new gene, designated MIDI, which encodes an N-glycosylated, integral plasma membrane protein with 548 amino acid residues. The mid)-) mutant has low Ca21 uptake activity, loses viability after receiving mating pheromones, and escapes death when incubated with high concentrations of CaCl2. The MID) gene is nonessential for vegetative growth. The efficiency of mating between AL4Ta mid)-) and MATa mid)-) cells is low. These results demonstrate that MID) is required for Ca2+ influx and mating.

An Osmotically Induced Cytosolic Ca2+ Transient Activates Calcineurin Signaling to Mediate Ion Homeostasis and Salt Tolerance of Saccharomyces cerevisiae

“…Cch1p contains four repeated peptide domains, each with sequence similarity to the ␣ 1 pore-forming subunit of L-type voltage-gated Ca 2ϩ channels (28). Mid1p is an N-glycosylated, integral plasma membrane protein inferred to be a Ca 2ϩ -permeable stretch-activated nonselective cation channel (26,28).…”

Cch1 and Mid1 Are Functionally Required for Vegetative Growth under Low-Calcium Conditions in the Phytopathogenic Ascomycete Botrytis cinerea

“…There is evidence that Mid1 is N glycosylated in the ER and is then transported to the plasma membrane. The channel is active in both the plasma membrane and the ER membrane (13,15,16), which is supported by the presence of a putative N-terminal signal peptide and several potential transmembrane (TM) ␣-helices. Different features, including an EF-hand domain for Ca 2ϩ binding and two cysteine-rich regions at the C terminus, are thought to be important for Mid1 function and seem to be involved in regulating Mid1 activity (13,17,18).…”

“…The channel is active in both the plasma membrane and the ER membrane (13,15,16), which is supported by the presence of a putative N-terminal signal peptide and several potential transmembrane (TM) ␣-helices. Different features, including an EF-hand domain for Ca 2ϩ binding and two cysteine-rich regions at the C terminus, are thought to be important for Mid1 function and seem to be involved in regulating Mid1 activity (13,17,18). Up to four hydrophobic regions were found to be partially conserved in S. cerevisiae, Neurospora crassa, and Magnaporthe grisea Mid1 homologs, a number similar to those in other known ion channels (19).…”

“…In yeast, Cch1 is localized in the plasma membrane, where it forms a complex with Mid1. Both proteins have been shown to be required for the uptake of extracellular Ca 2ϩ in cells responding to mating pheromones (13,(21)(22)(23)(24).…”

“…Mid1 is a mechanical, stretch-activated calcium-permeable nonselective cation channel (13,14) that was first discovered in Saccharomyces cerevisiae. Stretch-activated channels can be activated by deformation of cells.…”