MAP1B coordinates microtubule and actin filament remodeling in adult mouse Schwann cell tips and DRG neuron growth cones.

We previously described the function of MAP1B in both turning and branching of regenerating neurites. Our results suggested implication of MAP1B in coupling of actin and microtubule movements, a hypothesis investigated here using DRG neurons and Schwann cells (SCs), which also transiently express MAP1B. Cell motility and cytoskeletal rearrangements were assessed before and after addition of lysophosphatidic acid (LPA), an extracellular signaling phospholipid triggering changes in actin distribution and cell morphology. First, we show that MAP1B is required for SC migration in vitro, extending our previous work on its function in growth cone motility. Second, LPA stimulation induces drastic retraction of processes from MAP1B-expressing cells in a two-step process: actin contraction, which is followed by microtubule backfolding. More importantly, we provide evidence that MAP1B is required for microtubule backfolding, thereby unravelling an important molecular mechanism implicated in coupling the movements of actin and microtubules during process retraction of neural cells.