Acts as a 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. Mediates the recruitment of the WASH core complex to endosome membranes via binding to phospholipids and VPS35 of the retromer CSC. Mediates the recruitment of the F-actin-capping protein dimer to the WASH core complex probably promoting localized F-actin polymerization needed for vesicle scission (PubMed:19922874, PubMed:20498093, PubMed:22513087, PubMed:23331060). Via its C-terminus binds various phospholipids, most strongly phosphatidylinositol 4-phosphate (PtdIns-(4)P), phosphatidylinositol 5-phosphate (PtdIns-(5)P) and phosphatidylinositol 3,5-bisphosphate (PtdIns-(3,5)P2). Involved in the endosome-to-plasma membrane trafficking and recycling of SNX27-retromer-dependent cargo proteins, such as GLUT1 (PubMed:25278552). Required for the association of DNAJC13, ENTR1, ANKRD50 with retromer CSC subunit VPS35 (PubMed:24980502). Required for the endosomal recruitment of CCC and retriever complexes subunits COMMD1 and CCDC93 as well as the retrievere complex subunit VPS35L (PubMed:25355947, PubMed:28892079). {ECO:0000269|PubMed:19922874, ECO:0000269|PubMed:20498093, ECO:0000269|PubMed:22513087, ECO:0000269|PubMed:23331060, ECO:0000269|PubMed:24980502, ECO:0000269|PubMed:25278552, ECO:0000269|PubMed:25355947, ECO:0000269|PubMed:28892079}. (Microbial infection) Plays a role in fluid-phase endocytosis, a process exploited by vaccinia intracellular mature virus (IMV) to enter cells. As a result, may facilitate the penetration of IMV into cells. . This is the function of WASHC2C (WASH complex subunit 2C, ENSG00000172661).