Daam1 negatively regulates USP10 activity

The differentiation of fibroblasts into pathological myofibroblasts during wound healing is in part characterized by increased cell surface expression of αv-integrins. Our previous studies found that the deubiquitinase (DUB) USP10 removes ubiquitin from αv-integrins, leading to cell surface integrin accumulation, subsequent TGFβ1 activation, and myofibroblast differentiation. In this study, a yeast-two hybrid screen elucidated a novel binding partner for USP10, the formin, Daam1. The USP10/Daam1 interaction was also supported by proximity ligation assay (PLA) activity. Treatment with TGFβ1 significantly increased USP10 and Daam1 protein expression, PLA signal, and co-localization to actin stress fibers. Furthermore, Daam1 siRNA knockdown significantly reduced a) co-precipitation of USP10 and Daam1 on purified actin stress fibers, and b) β1- and β5-integrin ubiquitination resulting in increased αv-, β1-, and β5-integrin total protein levels, αv integrin recycling to the cell surface, and extracellular fibronectin (FN) organization. Together, our data suggest that Daam1 negatively regulates USP10’s DUB activity and subsequently maintains integrin protein homeostasis. ### Competing Interest Statement The authors have declared no competing interest.