Actomyosin-dependent Microtubule Rearrangement in Lysophosphatidic Acid-induced Neurite Remodeling of Young Cortical Neurons

It has been shown that lysophosphatidic acid (LPA), a signaling phospholipid, induces neurite retraction and the formation of retraction fibers in young cortical neurons by actin rearrangement. This study examined the rearrangement of microtubules (MTs) during LPA-induced neurite remodeling by immunostaining with antibodies against several types of tubulin. The results showed that alpha-tubulin was present in growing neurites as well as in cell bodies with various localization profiles. Exposure of neurons to LPA resulted in neurite retraction, accompanied by the rearrangement of MTs in neurites and the accumulation of MTs in cell bodies, without significant changes in the total amount of MTs in the cytoskeletal fraction of cultured neurons. Similar findings were obtained when young neurons were stained for other types of tubulin, including beta-tubulin type III and posttranslationally acetylated and tyrosinated tubulin. LPA-induced MT rearrangement was accompanied by accumulation of myosin IIB and polymerized actin at the base of retraction fibers. These effects of LPA on MTs and myosin IIB were blocked by pretreatment with inhibitors of the actomyosin and Rho pathways (cytochalasin D, blebbistatin, and Y27632), but not by an MT stabilizer (taxol), whereas taxol inhibited neurite retraction and MT depolymerization induced by nocodazole. Furthermore, neurofilaments also showed rearrangement in response to LPA, which was blocked by cytochalasin D and Y27632, but not taxol. Taken together, these results suggested that LPA did not induce MT depolymerization and that LPA-induced actomyosin activation produced MT and neurofilament rearrangement, leading to neurite remodeling.