Date: 27.10.2023, Time: 15:30h

Location moved to: Lecture Room B052, Theresienstr. 39, LMU
The talk will also be streamed online.

Saprophytic fungi rely on the uptake of a wide range of organic materials as nutrients and energy source. To achieve this task yeast cells have evolved a large arsenal of membrane transporters that are tightly regulated in their expression, localization and activity. We and others could previously show that the endocytic turnover of several yeast amino acid transporters is blocked by their lateral segregation into a unique invaginated domain of the plasma membrane (PM).

We now identified a novel function for the Sur7 family of tetraspanner proteins in the regulation of local PM topography. Combining TIRF imaging, STED nanoscopy, freeze-fracture EM and membrane simulations we found that Sur7 tetraspanners form multimeric strands at the edges of PM furrows, where they modulate forces exerted by BAR domain proteins at the furrow base. Loss of Sur7 tetraspanners or Sur7 displacement due to altered PIP2 homeostasis or changes in membrane fluidity led to increased PM invagination and a distinct form of membrane tubulation. Topographic defects, as well as the physiological consequences associated with PM tubulation were rescued by synthetic anchoring of Sur7 to furrows.

Our findings suggest a key role for tetraspanner proteins in sculpting local membrane domains. The maintenance of stable PM furrows depends on a balance between negative curvature at the base, which is generated by BAR domains, and positive curvature at the furrows´ edges, which is stabilized by strands of Sur7 tetraspanners.

I will also discuss how gel-like properties of the yeast PM can sustain the high forces associated with PM invaginations and how this supports formation of unusually stable lateral segregation patterns of a patchwork membrane.