Msb2 is a Ste11 membrane concentrator required for full activation of the HOG pathway.

The high osmolarity glycerol (HOG) pathway, composed of membrane-associated osmosensors, adaptor proteins and core signaling kinases, is essential for the survival of yeast cells under hyper-osmotic stress. Here, we studied how the MAPKKK Ste11 might change its protein interaction profile during acute stress exposure, with an emphasis on the sensory system of the so-called Sho1/Msb2 signaling branch. To characterize the transience of protein-protein interactions we utilized a recently described enzymatic in vivo protein proximity assay (M-track). Accordingly, interaction signals between Ste11 and many of its signaling partners can already be detected even under basal conditions. In most cas…