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.



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.

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.

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.

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.

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.


TC#NameOrganismal TypeExample

Slg1 or Wsc1 of 378 aas and probably two TMSs, one N-terminal and a second at residue 270 near the C-terminus. It is a mechanosensor (see Family description, paragraph 2 for details).

Slg1 of Saccharomyces cerevisiae


Uncharacterized protein of 718 aas and 1 or 2 TMSs, a large hydrophobic peak at residue 480, and a small peak at 530.

UP of Mytilus coruscus


Uncharacterized protein of 278 aas and 2 TMSs, one N-terminal and one at residue 210.

UP of Dothidotthia symphoricarpi


Uncharacterized protein of 405 aas and 2 TMSs, one N-terminal and one at residue 240.

UP of Pyricularia pennisetigena