Doublecortin induces mitotic microtubule catastrophe and inhibits glioma cell invasion

Abstract

Doublecortin (DCX) is a microtubule (MT) binding protein that induces growth arrest at the G2-M phase of cell cycle in glioma and suppresses tumor xenograft in immunocompromised hosts. DCX expression was found in neuronal cells, but lacking in glioma cells. We tested the hypothesis that DCX inhibits glioma U87 cell mitosis and invasion. Our data showed that DCX synthesizing U87 cells underwent mitotic MT spindle catastrophe in a neurabin II dependent pathway. Synthesis of both DCX and neurabin II were required to induce apoptosis in U87 and human embryonic kidney 293T cells. In DCX expressing U87 cells, association of phosphorylated DCX with protein phosphatase-1 (PP1) in the cytosol disrupted the interaction between kinesin-13 and PP1 in the nucleus and yielded spontaneously active kinesin-13. The activated kinesin-13 caused mitotic MT catastrophe in spindle checkpoint. Phosphorylated-DCX induced depolymerization of actin filaments in U87 cells, down-regulated matrix metalloproteinases-2 and -9, and inhibited glioma U87 cell invasion in a neurabin II dependent pathway. Thus, localization of the DCX-neurabin II-PP1 complex in the cytosol of U87 tumor cells inhibited PP1 phosphatase activities leading to antiglioma effects via (1) mitotic MT spindle catastrophe that blocks mitosis and (2) depolymerization of actin that inhibits glioma cell invasion.

Spinophilin acts as a tumor suppressor by regulating Rb phosphorylation

“…In line with this behavior, SPN has been shown to bind to the PP1-doublecortin complex, inducing its dephosphorylation 43 and inhibiting anchorage-independent growth in glioma cells. [44][45][46] In contrast, doublecortin-mediated growth repression is lost in the absence of Spn.…”

The antihelmintic flubendazole inhibits microtubule function through a mechanism distinct from Vinca alkaloids and displays preclinical activity in leukemia and myeloma

“…19 A more detailed description of the assessment of mitotic catastrophe is presented in the supplemental Methods.…”

Doublecortin (Dcx) Family Proteins Regulate Filamentous Actin Structure in Developing Neurons

“…Other studies have also suggested a role for Dcx in mediating the cross talk between the actin and microtubule cytoskeleton (Tsukada et al, 2005; Coquelle et al, 2006; Bielas et al, 2007; Santra et al, 2009). However, changes in the actin structure/function in Dcx mutant or RNAi treated neurons have not previously been reported, most likely because the actin phenotype is not as severe in single mutants compared with Dcx−/y; Dclk1−/− neurons.…”