Roland Wedlich-Söldner, Universität Münster

Leuchs-Russell-Auditorium, A.1.500, Staudtstr. 2

Location details

Abstract:

The formin INF2 is a unique actin nucleator that supports the transient mobilization of actin during the Calcium-mediated actin reset (CaAR) reaction. While global activation via binding to calcium-calmodulin can explain the dominant activity of INF2 over other nucleators, this also raises the challenge of how INF2 activity can be efficiently terminated. The risk of excessive activity can be seen in the large number of INF2 variants that have been linked to kidney and neuronal pathologies. We now show by combining quantitative live cell imaging with in vitro biochemistry and cryoEM results that the N-terminus of INF2 restricts activity not only via the canonical intramolecular DID-DAD autoinhibition but also via its binding to the side of the actin filament generated by the formin. In vivo single molecule experiments demonstrate that side binding physically stops INF2-mediated actin elongation but also increases the efficiency of intramolecular INF2-autoinhibition. The INF2-F-actin interaction provides an intrinsic negative feedback by product-inhibition that robustly limits INF2-mediated actin polymerization. Specific interference with actin side binding leads to prolonged INF2 activity upon calcium stimulation, prevents polarized reorganization of actin during plasma membrane repair, leads to deregulated activation of transcription and perturbs the organization of nephrocytes in Drosophila.