Role of myosin II activity and the regulation of myosin light chain phosphorylation in astrocytomas. 2008

Bodour Salhia, and Jeong Hyun Hwang, and Christian A Smith, and Mitsutoshi Nakada, and Fiona Rutka, and Marc Symons, and James T Rutka
The Arthur and Sonia Labatt Brain Tumor Research Center, The Hospital for Sick Children, The University of Toronto, Toronto, Ontario, Canada.

The generation of contractile force mediated by actin-myosin interactions is essential for cell motility. Myosin activity is promoted by phosphorylation of myosin light chain (MLC). MLC phosphorylation in large part is controlled by kinases that are effectors of Rho family GTPases. Accordingly, in this study we examined the effects of ROCK and Rac1 inhibition on MLC phosphorylation in astrocytoma cells. We found that low concentrations of the ROCK inhibitor Y27632 increased the phosphorylation state of the Triton X-100 soluble fraction of MLC, whereas higher concentrations of Y27632 decreased soluble phospho-MLC. These effects of Y27632 were dependent on Rac1. The soluble form of phospho-MLC comprises about 10% of total phospho-MLC in control cells. Interestingly, ROCK inhibition led to a decrease in the phosphorylation state of total MLC, whereas Rac1 inhibition had little effect. Thus, the soluble form of MLC is differentially regulated by ROCK and Rac1 compared with MLC examined in a total cell extract. We also observed that astrocytoma migration is stimulated by low concentrations of the myosin II inhibitor blebbistatin. However, higher concentrations of blebbistatin inhibit migration leading us to believe that migration has a biphasic dependence on myosin II activity. Taken together, our data show that modulation of myosin II activity is important in determining optimal astrocytoma migration. In addition, these findings suggest that there are at least two populations of MLC that are differentially regulated.

UI MeSH Term Description Entries
D010766 Phosphorylation The introduction of a phosphoryl group into a compound through the formation of an ester bond between the compound and a phosphorus moiety. Phosphorylations
D002465 Cell Movement The movement of cells from one location to another. Distinguish from CYTOKINESIS which is the process of dividing the CYTOPLASM of a cell. Cell Migration,Locomotion, Cell,Migration, Cell,Motility, Cell,Movement, Cell,Cell Locomotion,Cell Motility,Cell Movements,Movements, Cell
D006801 Humans Members of the species Homo sapiens. Homo sapiens,Man (Taxonomy),Human,Man, Modern,Modern Man
D001254 Astrocytoma Neoplasms of the brain and spinal cord derived from glial cells which vary from histologically benign forms to highly anaplastic and malignant tumors. Fibrillary astrocytomas are the most common type and may be classified in order of increasing malignancy (grades I through IV). In the first two decades of life, astrocytomas tend to originate in the cerebellar hemispheres; in adults, they most frequently arise in the cerebrum and frequently undergo malignant transformation. (From Devita et al., Cancer: Principles and Practice of Oncology, 5th ed, pp2013-7; Holland et al., Cancer Medicine, 3d ed, p1082) Astrocytoma, Subependymal Giant Cell,Glioma, Astrocytic,Oligoastrocytoma, Mixed,Pleomorphic Xanthoastrocytomas,Anaplastic Astrocytoma,Astrocytoma, Grade I,Astrocytoma, Grade II,Astrocytoma, Grade III,Astrocytoma, Protoplasmic,Astroglioma,Cerebral Astrocytoma,Childhood Cerebral Astrocytoma,Fibrillary Astrocytoma,Gemistocytic Astrocytoma,Intracranial Astrocytoma,Juvenile Pilocytic Astrocytoma,Pilocytic Astrocytoma,Subependymal Giant Cell Astrocytoma,Anaplastic Astrocytomas,Astrocytic Glioma,Astrocytic Gliomas,Astrocytoma, Anaplastic,Astrocytoma, Cerebral,Astrocytoma, Childhood Cerebral,Astrocytoma, Fibrillary,Astrocytoma, Gemistocytic,Astrocytoma, Intracranial,Astrocytoma, Juvenile Pilocytic,Astrocytoma, Pilocytic,Astrocytomas,Astrocytomas, Grade III,Astrogliomas,Cerebral Astrocytoma, Childhood,Cerebral Astrocytomas,Childhood Cerebral Astrocytomas,Fibrillary Astrocytomas,Gemistocytic Astrocytomas,Gliomas, Astrocytic,Grade I Astrocytoma,Grade I Astrocytomas,Grade II Astrocytoma,Grade II Astrocytomas,Grade III Astrocytoma,Grade III Astrocytomas,Intracranial Astrocytomas,Juvenile Pilocytic Astrocytomas,Mixed Oligoastrocytoma,Mixed Oligoastrocytomas,Pilocytic Astrocytoma, Juvenile,Pilocytic Astrocytomas,Pleomorphic Xanthoastrocytoma,Protoplasmic Astrocytoma,Protoplasmic Astrocytomas,Xanthoastrocytoma, Pleomorphic
D045744 Cell Line, Tumor A cell line derived from cultured tumor cells. Tumor Cell Line,Cell Lines, Tumor,Line, Tumor Cell,Lines, Tumor Cell,Tumor Cell Lines
D054460 rho-Associated Kinases A group of intracellular-signaling serine threonine kinases that bind to RHO GTP-BINDING PROTEINS. They were originally found to mediate the effects of rhoA GTP-BINDING PROTEIN on the formation of STRESS FIBERS and FOCAL ADHESIONS. Rho-associated kinases have specificity for a variety of substrates including MYOSIN-LIGHT-CHAIN PHOSPHATASE and LIM KINASES. rho-Associated Kinase,ROCK Protein Kinases,ROCK-I Protein Kinase,ROCK-II Protein Kinase,ROK Kinase,p160 rhoA-Binding Kinase ROKalpha,p160ROCK,rho-Associated Coiled-Coil Containing Protein Kinase 1,rho-Associated Coiled-Coil Containing Protein Kinase 2,rho-Associated Coiled-Coil Kinase,rho-Associated Kinase 1,rho-Associated Kinase 2,rho-Associated Kinase alpha,rho-Associated Kinase beta,rho-Associated Protein Kinase alpha,rho-Associated Protein Kinase beta,rho-Kinase,Coiled-Coil Kinase, rho-Associated,Protein Kinases, ROCK,ROCK I Protein Kinase,ROCK II Protein Kinase,p160 rhoA Binding Kinase ROKalpha,rho Associated Coiled Coil Containing Protein Kinase 1,rho Associated Coiled Coil Containing Protein Kinase 2,rho Associated Coiled Coil Kinase,rho Associated Kinase,rho Associated Kinase 1,rho Associated Kinase 2,rho Associated Kinase alpha,rho Associated Kinase beta,rho Associated Kinases,rho Associated Protein Kinase alpha,rho Associated Protein Kinase beta,rho Kinase
D018994 Myosin Light Chains The smaller subunits of MYOSINS that bind near the head groups of MYOSIN HEAVY CHAINS. The myosin light chains have a molecular weight of about 20 KDa and there are usually one essential and one regulatory pair of light chains associated with each heavy chain. Many myosin light chains that bind calcium are considered "calmodulin-like" proteins. Myosin Alkali Light Chains,Myosin Alkali Light Chain,Myosin Essential Light Chain,Myosin Essential Light Chains,Myosin Light Chain,Myosin Regulatory Light Chain,Myosin Regulatory Light Chains,Light Chain, Myosin,Light Chains, Myosin
D020830 rac1 GTP-Binding Protein A rac GTP-binding protein involved in regulating actin filaments at the plasma membrane. It controls the development of filopodia and lamellipodia in cells and thereby influences cellular motility and adhesion. It is also involved in activation of NADPH OXIDASES. This enzyme was formerly listed as EC 3.6.1.47. TC-25 GTP-Binding Protein,rac1 Protein,ras-Related C3 Botulinum Toxin Substrate 1,GTP-Binding Protein, TC-25,GTP-Binding Protein, rac1,TC 25 GTP Binding Protein,rac1 GTP Binding Protein,ras Related C3 Botulinum Toxin Substrate 1
D024462 Myosin Type II The subfamily of myosin proteins that are commonly found in muscle fibers. Myosin II is also involved a diverse array of cellular functions including cell division, transport within the GOLGI APPARATUS, and maintaining MICROVILLI structure. Myosin II

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