Dissecting WHAMM-mediated Membrane Deformation

The microtubule?MT?and actin cytoskeletons are well studied systems within eu-karyotic cells that govern multiple aspects of cellular functions,including cell division,migration,cell morphology,and intracellular vesicle transportation.Among these cellu-lar events,membrane trafficking coordinated by the two systems is a major process but remains largely under-studied.In recent years,multiple proteins are discovered to be involved in cytoskeleton-coordinated membrane trafficking or remodeling.WHAMM?abbreviated for WASP Homolog associated with Actin,Membranes,and Microtubules?is one of the typical proteins with this function.WHAMM is a mammalian protein belonging to the WASP-family of ac-tin-polymerization nucleation promoting factors?NPFs?.WHAMM comprises of mul-tiple domains that harbor functions to interact with membrane?WMD domain?,bind to microtubules?CC domain?,and promote Arp2/3 mediated actin-polymerization?PWCA domain?.In a cell,WHAMM mostly localizes near ER and Golgi apparatus and is criti-cal to maintain the shape of Golgi and mediate intracellular vesicle transportation from ER to Golgi.Previous work has defined a coordination mechanism for the multiple domains of WHAMM in membrane tubulation.In this work,we further dissected the specific ele-ments in WHAMM responsible for recognizing membranes and binding to microtubules.We performed systematic analysis of WHAMM's interaction with liposomes containing different lipids to identify the major phospholipids involved in WHAMM's membrane interaction and found that WHAMM preferentially recognizes PI?4,5?P₂ lipids in the membrane in a density dependent manner.We also identified a binding motif in WHAMM for specific interaction with tubulin dimer in microtubules and determined the structure of WHAMM-MT interaction moiety at near atomic resolution.The identi-fication of specific elements for WHAMM's interaction with membranes and microtu-bules provides new insight into the coordinated activities of WHAMM on various self-assembly systems involved in membrane trafficking and remodeling.