Regulation of microfilament organization by Kaposi sarcoma-associated herpes virus-cyclin.CDK6 phosphorylation of caldesmon.
Kaposi sarcoma-associated herpes virus (KSHV) encodes a D-like cyclin (K-cyclin) that is thought to contribute to the viral oncogenicity. K-cyclin activates cellular cyclin-dependent kinases (CDK) 4 and 6, generating enzymes with a substrate selectivity deviant from CDK4 and CDK6 activated by D-type cyclins, suggesting different biochemical and biological functions. Here we report the identification of the actin- and calmodulin-binding protein caldesmon (CALD1) as a novel K-cyclin.CDK substrate, which is not phosphorylated by D.CDK. CALD1 plays a central role in the regulation of microfilament organization, consequently controlling cell shape, adhesion, cytokinesis and motility. K-cyclin.CDK6 specifically phosphorylates four Ser/Thr sites in the human CALD1 carboxyl terminus, abolishing CALD1 binding to its effector protein, actin, and its regulator protein, calmodulin. CALD1 is hyperphosphorylated in cells following K-cyclin expression and in KSHV-transformed lymphoma cells. Moreover, expression of exogenous K-cyclin results in microfilament loss and changes in cell morphology; both effects are reliant on CDK catalysis and can be reversed by the expression of a phosphorylation defective CALD1. Together, these data strongly suggest that K-cyclin expression modulates the activity of caldesmon and through this the microfilament functions in cells. These results establish a novel link between KSHV infection and the regulation of the actin cytoskeleton.
Cuomo
Maria Emanuela
ME
Cancer Research UK Centre for Cell and Molecular Biology, Chester Beatty Laboratories, The Institute of Cancer Research, 237 Fulham Road, SW3 6JB London, United Kingdom.
Knebel
Axel
A
Platt
Georgina
G
Morrice
Nick
N
Cohen
Philip
P
Mittnacht
Sibylle
S
D000199:Actins / Q000737:chemistry; D000818:Animals; D002148:Calmodulin-Binding Proteins / Q000737:chemistry* / Q000378:metabolism; D002384:Catalysis; D002846:Chromatography, Affinity; D003001:Cloning, Molecular; D051358:Cyclin-Dependent Kinase 4 / Q000378:metabolism; D051361:Cyclin-Dependent Kinase 6 / Q000378:metabolism*; D003599:Cytoskeleton / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D015967:Gene Expression Regulation, Viral; D006367:HeLa Cells; D019288:Herpesvirus 8, Human / Q000378:metabolism*; D006801:Humans; D013058:Mass Spectrometry; D051379:Mice; D008856:Microscopy, Fluorescence; D041681:NIH 3T3 Cells; D010455:Peptides / Q000737:chemistry; D010766:Phosphorylation; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D034741:RNA, Small Interfering / Q000378:metabolism; D011994:Recombinant Proteins / Q000737:chemistry; D016160:Retinoblastoma Protein / Q000378:metabolism; D012685:Sepharose / Q000737:chemistry; D012694:Serine / Q000737:chemistry; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D013379:Substrate Specificity; D013912:Threonine / Q000737:chemistry; D013997:Time Factors
D000199:Actins; D002148:Calmodulin-Binding Proteins; D010455:Peptides; D034741:RNA, Small Interfering; D011994:Recombinant Proteins; D016160:Retinoblastoma Protein; D013912:Threonine; D012694:Serine; D012685:Sepharose; C495900:CDK4 protein, human; D051358:Cyclin-Dependent Kinase 4; D051361:Cyclin-Dependent Kinase 6