Recruitment of the endosomal WASH complex is mediated by the extended ‘tail’ of Fam21 binding to the retromer protein Vps35

Abstract

The retromer complex is a conserved endosomal protein sorting complex that sorts membrane proteins into nascent endosomal tubules. The recognition of membrane proteins is mediated by the cargo-selective retromer complex, a stable trimer of the Vps35 (vacuolar protein sorting 35), Vps29 and Vps26 proteins. We have recently reported that the cargo-selective retromer complex associates with the WASH (Wiskott-Aldrich syndrome homologue) complex, a multimeric protein complex that regulates tubule dynamics at endosomes. In the present study, we show that the retromer-WASH complex interaction occurs through the long unstructured 'tail' domain of the WASH complex-Fam21 protein binding to Vps35, an interaction that is necessary and sufficient to target the WASH complex to endosomes. The Fam21-tail also binds to FKBP15 (FK506-binding protein 15), a protein associated with ulcerative colitis, to mediate the membrane association of FKBP15. Elevated Fam21-tail expression inhibits the association of the WASH complex with retromer, resulting in increased cytoplasmic WASH complex. Additionally, overexpression of the Fam21-tail results in cell-spreading defects, implicating the activity of the WASH complex in regulating the mobilization of membrane into the endosome-to-cell surface pathway.

A mechanism for retromer endosomal coat complex assembly with cargo

“…3D) and is contained within the minimal segment of VPS35 that assembles with VPS26 (19,20). These results confirm and extend a recent yeast two-hybrid study that reported that SNX3 can interact with the N-terminal half of VPS35 (21). The N-terminal ∼300 aa of VPS35 containing the binding sites for VPS26, SNX3, and RAB7 comprise its most highly conserved region, underscoring the critical roles that, as we show below, SNX3 and RAB7 play in retromer recruitment to a membrane.…”

Endosomal sorting of Notch receptors through COMMD9-dependent pathways modulates Notch signaling

“…Furthermore, silencing of CCDC93 or C16orf62 (two additional components of the CCC complex) also led to reduced plasma membrane staining for Notch2, a pattern also observed on silencing of VPS35 (Fig. S3, A and B), a subunit of the retromer complex which is important for WASH recruitment and function (Harbour et al, 2012;Jia et al, 2012). Altogether, these findings indicate that the absence of COM MD9 and associated factors results in the accumulation of Notch2 in the early endosomal compartment.…”

“…This COM MD-CCDC22-CCDC93 (CCC) complex localizes to endosomes through interactions between CCDC22 and CCDC93 with FAM21 (Harbour et al, 2012;Freeman et al, 2014;Phillips-Krawczak et al, 2015), a component of the Wiskott-Aldrich syndrome protein and scar homolog (WASH) complex (Derivery et al, 2009;Gomez and Billadeau, 2009). WASH is a member of the Wiskott-Aldrich syndrome protein Notch family members are transmembrane receptors that mediate essential developmental programs.…”

Cellular functions of WASP family proteins at a glance

“…WASH is recruited to retromer-positive endosomal subdomains via the interaction of the extended C-terminal tail of FAM21 with the retromer subunit VPS35 (Harbour et al, 2012;Jia et al, 2012). Interestingly, a mutation in VPS35 (D620N) (Vilariño-Güell et al, 2011;Zimprich et al, 2011) that is associated with earlyonset Parkinson's disease has been shown to diminish the interaction of the SHRC with VPS35 and impair vesicular trafficking from the late endosome (Follett et al, 2013;McGough et al, 2014;Zavodszky et al, 2014).…”

“…WASH localizes to endosomes (Derivery et al, 2009;Gomez and Billadeau, 2009;Harbour et al, 2012;Jia et al, 2012;Monfregola et al, 2010;Monteiro et al, 2013;Ryder et al, 2013), and WASHgenerated F-actin not only regulates the architecture of the endolysosomal system, but also spares specific cargo from lysosomal degradation or missorting (Bartuzi et al, 2016;Derivery et al, 2009Derivery et al, , 2012Duleh and Welch, 2010;Gomez and Billadeau, 2009;Gomez et al, 2012;Monteiro et al, 2013;Zech et al, 2011). WASH is recruited to retromer-positive endosomal subdomains via the interaction of the extended C-terminal tail of FAM21 with the retromer subunit VPS35 (Harbour et al, 2012;Jia et al, 2012).…”