Abstract
Neurons are highly polarized cells that possess two morphologically and functionally different types of protrusions, axons and dendrites, that function in the transmission and reception of neural signals, respectively. A great deal of attention has been paid to the specification and guidance of axons, but the mechanism of dendrite development remains mostly unknown. We report here that a polarity-regulating kinase, partitioning-defective 1 (Par1b)/microtubule affinity-regulating kinase 2 (MARK2), specifically regulates development of dendrites in hippocampal neurons. Ectopic expression of Par1b/MARK2 shortens the length and decreases branching of dendrites without significant effects on axons. Knockdown of endogenous Par1b/MARK2 by RNA interference stimulates dendrite development. Wnt stimulation and Dishevelled expression, both of which are known to induce dendrite development, induced recruitment of Par1b/MARK2 to the membrane fraction. Expression of a Par1b/MARK2 mutant, that contains a myristoylation signal and accumulates exclusively in membranes, does not affect dendrite development. In addition, Par1b/MARK2 efficiently phosphorylated MAP2, which is localized mainly in dendrites. These results indicate that Par1b/MARK2 negatively regulates dendrite development through phosphorylation of MAP2.