Myosin 1c participates in B cell cytoskeleton rearrangements, is recruited to the immunological synapse and contributes to antigen presentation. (100.48)

Abstract Myosin 1c (Myo1c) is a member of the unconventional class I myosins of vertebrates, which directly link the plasma membrane with the microfilament cortical web. Although this molecular motor has been implicated in cell functions such as cytoskeleton organization, cell motility, nuclear transcription and endocytosis; its role in the hematopoietic cells is largely unknown. We found that Myo1c is abundantly expressed in murine B lymphocytes and is preferentially located at the plasma membrane, especially in peripheral processes such as microvilli. It was observed not only that this motor concentrates at the growing membrane protrusions generated during B cell spreading, but also that is actively recruited to the immune synapse. Interestingly, Myo1c was detected in the lipid rafts of B cells and showed a strong colocalization with MHC-II, particularly after crosslinking of these molecules. By transfecting a dominant negative form of Myo1c, we also detected alterations in spreading and antigen presentation ability of these cells. All these data suggest that Myo1c could be involved in the B lymphocyte cytoskeleton dynamics and membrane protein anchoring and/or sorting, during cell-cell contacts, including those related with CD4+ T cell activation.