title: MARCKS actin-binding capacity mediates actin filament assembly during mitosis in human hepatic stellate cells.
abstract: Cross-linking between the actin cytoskeleton and plasma membrane actin-binding proteins is a key interaction responsible for the mechanical properties of the mitotic cell. Little is known about the identity, the localization, and the function of actin filament-binding proteins during mitosis in human hepatic stellate cells (hHSC). The aim of the present study was to identify and analyze the cross talk between actin and myristoylated alanine-rich kinase C substrate (MARCKS), an important PKC substrate and actin filament-binding protein, during mitosis in primary hHSC. Confocal analysis and chromosomal fraction analysis of mitotic hHSC demonstrated that phosphorylated (P)-MARCKS displays distinct phase-dependent localizations, accumulates at the perichromosomal layer, and is a centrosomal protein belonging to the chromosomal cytosolic fraction. Aurora B kinase (AUBK), an important mitotic regulator, β-actin, and P-MARCKS concentrate at the cytokinetic midbody during cleavage furrow formation. This localization is critical since MARCKS-depletion in hHSC is characterized by a significant loss in cytosolic actin filaments and cortical β-actin that induces cell cycle inhibition and dislocation of AUBK. A depletion of AUBK in hHSC affects cell cycle, resulting in multinucleation. Quantitative live cell imaging demonstrates that the actin filament-binding capacity of MARCKS is key to regulate mitosis since the cell cycle inhibitory effect in MARCKS-depleted cells caused abnormal cell morphology and an aberrant cytokinesis, resulting in a significant increase in cell cycle time. These findings implicate that MARCKS, an important PKC substrate, is essential for proper cytokinesis and that MARCKS and its partner actin are key mitotic regulators during cell cycle in hHSC.
authors.affiliation: Department of Internal Medicine, University of Florence, Italy. k.rombouts@dmi.unifi.it
authors.forename: Krista
authors.initials: K
authors.lastname: Rombouts
authors.forename: Tommaso
authors.initials: T
authors.lastname: Mello
authors.forename: Francesco
authors.initials: F
authors.lastname: Liotta
authors.forename: Andrea
authors.initials: A
authors.lastname: Galli
authors.forename: Alessandra
authors.initials: A
authors.lastname: Caligiuri
authors.forename: Francesco
authors.initials: F
authors.lastname: Annunziato
authors.forename: Massimo
authors.initials: M
authors.lastname: Pinzani
mesh_terms: D000199:Actins / Q000378:metabolism*; D000906:Antibodies; D064107:Aurora Kinase B; D064127:Aurora Kinases; D002453:Cell Cycle; D049109:Cell Proliferation; D002478:Cells, Cultured; D018385:Centrosome / Q000502:physiology; D003599:Cytoskeleton / Q000502:physiology; D055166:Hepatic Stellate Cells / Q000166:cytology* / Q000378:metabolism*; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000235:genetics* / Q000378:metabolism*; D008565:Membrane Proteins / Q000235:genetics* / Q000378:metabolism*; D008938:Mitosis / Q000502:physiology; D000076250:Myristoylated Alanine-Rich C Kinase Substrate; D010766:Phosphorylation; D011485:Protein Binding; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism; D034622:RNA Interference; D013194:Staining and Labeling
chemical_list: D000199:Actins; D000906:Antibodies; D047908:Intracellular Signaling Peptides and Proteins; C000619710:MARCKS protein, human; D008565:Membrane Proteins; D000076250:Myristoylated Alanine-Rich C Kinase Substrate; C576921:AURKB protein, human; D064107:Aurora Kinase B; D064127:Aurora Kinases; D017346:Protein Serine-Threonine Kinases