Tos7 (Yol019w) is a Sur7/PalI family transmembrane protein in the budding yeast Saccharomyces cerevisiae. Since the deletion of TOS7 did not affect growth or cell morphology, the cellular roles of Tos7 have not been established previously. Here, we show that high-copy TOS7 expression suppressed the growth defect of the secretion-defective RGA1-C term-overexpressing mutant and sec15-1 mutant. Moreover, Tos7 physically interacted with Boi2 and the Rho GTPase Rho3, two key regulators of exocyst assembly, suggesting that Tos7 plays a role in secretion. We also show that the deletion of TOS7 rendered the cells more sensitive to the cell wall-disrupting agents Congo red and calcofluor white while high-copy TOS7 expression had an opposite effect, suggesting that Tos7 affects cell wall organization. Finally, we show that Tos7 localized to punctate patches on the plasma membrane that were largely co-localized with the plasma membrane microdomains named MCC (membrane compartment of Can1). Together, these results suggest that Tos7 contributes to cell surface-related functions. Tos7 is likely an auxiliary component of MCC/eisosome that specifically interacts with the secretory pathway.

Tos7 (Yol019w) 是出芽酵母酿酒酵母中的 Sur7/PalI 家族跨膜蛋白。由于TOS7的缺失不影响生长或细胞形态，因此之前尚未确定 Tos7 的细胞作用。在这里，我们表明高拷贝TOS7表达抑制了分泌缺陷RGA1 -C 术语过度表达突变体和sec15-1突变体的生长缺陷。此外，Tos7 与 Boi2 和 Rho GTPase Rho3（胞外囊组装的两个关键调节因子）发生物理相互作用，表明 Tos7 在分泌中起作用。我们还表明TOS7的删除使细胞对细胞壁破坏剂刚果红和calcofluor白更敏感，而高拷贝TOS7表达具有相反的效果，表明 Tos7 影响细胞壁组织。最后，我们表明 Tos7 定位为质膜上的点状斑块，这些斑块在很大程度上与称为 MCC（Can1 的膜隔室）的质膜微域共定位。总之，这些结果表明 Tos7 有助于细胞表面相关功能。Tos7 可能是 MCC/eisosome 的辅助成分，与分泌途径特异性相互作用。