Fig. 9.

Receptor protein tyrosine phosphatase (PTP) and Btk regulation of F-actin network integrities. a Schematic representation of the interplay between PTPs, Btk29A and WASH (Wiskott–Aldrich syndrome protein and SCAR homologue) in endocytosis. Btk29A promotes WASH activation by tyrosine phosphorylation while PTPs directly or indirectly antagonizes WASH. Active WASH induces the formation of endosomal actin patches via the Arp2/3 complex and promotes endocytosis. By contrast, DAAM and formins generate apical/cortical actin bundles¹² and maintain steady-state levels of endocytosis. The model proposes a direct competition between the WASH-Arp2/3 and formin-mediated polymerization modes for a globular actin pool (G-actin). b Cartoons showing the function of PTPs/Btk29A/WASH and actin bundles during luminal protein clearance in wild-type and Ptp4EPtp10D. EE early endosome