MAPK3 and astrocytoma (excluding glioblastoma): Since in U251 cells we recently revealed MLC1-mediated inhibition of phospho-ERK1/2 (pERK1/2) [29,30] that, in U251 cells, is constitutively activated [43], we hypothesized that MLC1 might indirectly alter Cx43 trafficking by inhibiting pERK1/2 activation in astrocytoma cells.