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9.B.454.  The Transmembrane Mechanosensor, Slg1 (Slg1) Family 

Slg1 plays a role during G1 to regulate entering or exiting the cell cycle (Ivanovska and Rose 2000, Lodder et al. 1999). It is involved in stress responses because it plays a role in cell wall integrity signaling; it activates ROM1 or ROM2 catalyzed guanine nucleotide exchange toward RHO1 and is an important regulator of the actin cytoskeleton rearrangements in conditions of cell wall expansion and membrane stretching (Philip and Levin 2001). Specifically, it is required for the actin reorganization induced by hypo-osmotic shock. It is also a multicopy suppressor of 1,3-beta-glucan synthase (GS), activating GS upstream of RHO1 (Sekiya-Kawasaki et al. 2002). It acts positively on the PKC1-MAPK pathway. It transiently activates SLT2 during alkaline stress, which leads to an increase in the expression of several genes.

In response to high hydrostatic pressure in the yeast Saccharomyces cerevisiae, the transmembrane mechanosensor Wsc1 (Slg1) and aquaglyceroporin Fps1 function in a general mechanism to maintain cell growth under high-pressure regimes (Mochizuki et al. 2023). The promotion of water influx into cells at 25 MPa causes an an increase in cell volume and a loss of the plasma membrane eisosome structure while activating the CWI pathway through the function of Wsc1. Phosphorylation of Slt2, the downstream mitogen-activated protein kinase, increased at 25 MPa. Glycerol efflux increases via Fps1 phosphorylation, which is initiated by downstream components of the CWI pathway and contributes to the reduction in intracellular osmolarity under high pressure. The elucidation of the mechanisms underlying adaptation to high pressure through the well-established CWI pathway might translate to mammalian cells (Mochizuki et al. 2023).

This family may be homologous to families 8.A.23 and 8.A.128 so these three families may conprise a Superfamily.

References associated with 9.B.454 family:

Ivanovska, I. and M.D. Rose. (2000). SLG1 plays a role during G1 in the decision to enter or exit the cell cycle. Mol. Gen. Genet. 262: 1147-1156. 10660075
Lodder, A.L., T.K. Lee, and R. Ballester. (1999). Characterization of the Wsc1 protein, a putative receptor in the stress response of Saccharomyces cerevisiae. Genetics 152: 1487-1499. 10430578
Mochizuki, T., T. Tanigawa, S. Shindo, M. Suematsu, Y. Oguchi, T. Mioka, Y. Kato, M. Fujiyama, E. Hatano, M. Yamaguchi, H. Chibana, and F. Abe. (2023). Activation of CWI pathway through high hydrostatic pressure, enhancing glycerol efflux via the aquaglyceroporin Fps1 in. Mol. Biol. Cell 34: ar92. 37379203
Philip, B. and D.E. Levin. (2001). Wsc1 and Mid2 are cell surface sensors for cell wall integrity signaling that act through Rom2, a guanine nucleotide exchange factor for Rho1. Mol. Cell Biol. 21: 271-280. 11113201
Sekiya-Kawasaki, M., M. Abe, A. Saka, D. Watanabe, K. Kono, M. Minemura-Asakawa, S. Ishihara, T. Watanabe, and Y. Ohya. (2002). Dissection of upstream regulatory components of the Rho1p effector, 1,3-β-glucan synthase, in Saccharomyces cerevisiae. Genetics 162: 663-676. 12399379