LIM kinase-mediated cofilin phosphorylation during mitosis is required for precise spindle positioning.
The interaction of astral microtubules with cortical actin networks is essential for the correct orientation of the mitotic spindle; however, little is known about how the cortical actin organization is regulated during mitosis. LIM kinase-1 (LIMK1) regulates actin dynamics by phosphorylating and inactivating cofilin, an actin-depolymerizing protein. LIMK1 activity increases during mitosis. Here we show that mitotic LIMK1 activation is critical for accurate spindle orientation in mammalian cells. Knockdown of LIMK1 suppressed a mitosis-specific increase in cofilin phosphorylation and caused unusual cofilin localization in the cell cortex in metaphase, instability of cortical actin organization and astral microtubules, irregular rotation and misorientation of the spindle, and a delay in anaphase onset. Similar results were obtained by treating the cells with a LIMK1 in hibitor peptide or latrunculin A or by overexpressing a non-phosphorylatable cofilin(S3A) mutant. Furthermore, localization of LGN (a protein containing the repetitive Leu-Gly-Asn tripeptide motifs), an important regulator of spindle orientation, in the crescent-shaped cortical regions was perturbed in LIMK1 knockdown cells. Our results suggest that LIMK1-mediated cofilin phosphorylation is required for accurate spindle orientation by stabilizing cortical actin networks during mitosis.
Kaji
Noriko
N
Department of Biomolecular Sciences, Graduate School of Life Sciences, Tohoku University, Sendai, Miyagi 980-8578, Japan.
Muramoto
Aya
A
Mizuno
Kensaku
K
D051339:Actin Depolymerizing Factors / Q000235:genetics / Q000378:metabolism*; D000199:Actins / Q000235:genetics / Q000378:metabolism; D019943:Amino Acid Substitution; D000705:Anaphase / Q000502:physiology*; D000818:Animals; D019086:Bridged Bicyclo Compounds, Heterocyclic / Q000494:pharmacology; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism; D018797:Cell Cycle Proteins; D006367:HeLa Cells; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000235:genetics / Q000378:metabolism; D054461:Lim Kinases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D008677:Metaphase / Q000502:physiology*; D051379:Mice; D008870:Microtubules / Q000235:genetics / Q000378:metabolism; D020125:Mutation, Missense; D010455:Peptides / Q000235:genetics / Q000494:pharmacology; D010766:Phosphorylation / Q000187:drug effects; D008941:Spindle Apparatus / Q000235:genetics / Q000378:metabolism*; D053778:Thiazolidines / Q000494:pharmacology
D051339:Actin Depolymerizing Factors; D000199:Actins; D019086:Bridged Bicyclo Compounds, Heterocyclic; D002352:Carrier Proteins; D018797:Cell Cycle Proteins; C102754:GPSM2 protein, human; D047908:Intracellular Signaling Peptides and Proteins; C502655:LGN protein, mouse; D010455:Peptides; D053778:Thiazolidines; C515892:LIMK1 protein, human; D054461:Lim Kinases; C515893:Limk1 protein, mouse; C037067:latrunculin A