Retromer-mediated endosomal protein sorting: all WASHed up!

• Localised actin patches on endosomes define discrete domains to facilitate protein sorting.
• Formation of branched actin on endosomes requires the WASH complex.
• The retromer complex recruits the WASH complex to endosomes.
• The WASH complex along with retromer sorts endosomal membrane proteins to multiple destinations.

Endosomal protein sorting governs the fate of many physiologically important proteins involved in a panoply of cellular functions. Recent discoveries have revealed a vital role for endosomally localised branched actin patches in facilitating protein sorting. The formation of the actin patches has been shown to require the function of the WASH complex – the major endosomal actin polymerisation-promoting complex – which stimulates the activity of the ubiquitously expressed Arp2/3 complex. Another key component of the endosomal protein-sorting machinery is the retromer complex. Studies now show that retromer mediates the recruitment of the WASH complex and its regulators to endosomes. In this review, recent progress in understanding the role of the WASH complex along with retromer in endosomal protein sorting is discussed.