Acts as component of the WASH core complex that functions as a nucleation-promoting factor (NPF) at the surface of endosomes, where it recruits and activates the Arp2/3 complex to induce actin polymerization, playing a key role in the fission of tubules that serve as transport intermediates during endosome sorting (PubMed:19922875). Regulates the trafficking of endosomal alpha5beta1 integrin to the plasma membrane and involved in invasive cell migration (PubMed:22114305). In T-cells involved in endosome-to-membrane recycling of receptors including T-cell receptor (TCR), CD28 and ITGAL; proposed to be implicated in T-cell proliferation and effector function (PubMed:23275443). In dendritic cells involved in endosome-to-membrane recycling of major histocompatibility complex (MHC) class II probably involving retromer and subsequently allowing antigen sampling, loading and presentation during T-cell activation (PubMed:24886983). Involved in cytokinesis and following polar body extrusion during oocyte meiotic maturation (PubMed:24998208). Involved in Arp2/3 complex-dependent actin assembly driving Salmonella typhimurium invasion independent of ruffling (PubMed:19732055). Involved in the exocytosis of MMP14 leading to matrix remodeling during invasive migration and implicating late endosome-to-plasma membrane tubular connections and cooperation with the exocyst complex (By similarity). Involved in negative regulation of autophagy independently from its role in endosomal sorting by inhibiting BECN1 ubiquitination to inactivate PIK3C3/Vps34 activity (PubMed:23974797). Component of the WASH core complex also described as WASH regulatory complex SHRC composed of WASHC1, WASHC2, WASHC3, WASHC4 and WASHC5. The WASH core complex associates with the F-actin-capping protein dimer (formed by CAPZA1, CAPZA2 or CAPZA3 and CAPZB) in a transient or substoichiometric manner which was initially described as WASH complex. Interacts (via WHD1 region) with WASHC2; the interaction is direct (By similarity). Interacts with BECN1; WASHC1 and AMBRA1 can competitively interact with BECN1 (PubMed:23974797). Interacts with BLOC1S2; may associate with the BLOC-1 complex. Interacts with tubulin gamma chain (TUBG1 or TUBG2) (PubMed:20308062). Interacts with TBC1D23 (PubMed:29084197). Localization to the endosome membrane is mediated via its interaction with WASHC2 (By similarity). Localized to Salmonella typhimurium entry sites (PubMed:19732055). Ubiquitously expressed. The VCA (verprolin, cofilin, acidic) domain promotes actin polymerization by the Arp2/3 complex in vitro. Ubiquitinated at Lys-219 via 'Lys-63'-linked ubiquitin chains by the TRIM27:MAGEL2 E3 ubiquitin ligase complex, leading to promote endosomal F-actin assembly. Belongs to the WASH1 family. Extended N-terminus.