title: Increased myocardial Rab GTPase expression: a consequence and cause of cardiomyopathy.
abstract: The Ras-like Rab GTPases regulate vesicle transport in endocytosis and exocytosis. We found that cardiac Rabs1, 4, and 6 are upregulated in a dilated cardiomyopathy model overexpressing beta(2)-adrenergic receptors. To determine if increased Rab GTPase expression can contribute to cardiomyopathy, we transgenically overexpressed in mouse hearts prototypical Rab1a, the small G protein that regulates vesicle transport from endoplasmic reticulum to and through Golgi. In multiple independent mouse lines, Rab1a overexpression caused cardiac hypertrophy that progressed in a time- and transgene dose-dependent manner to heart failure. Isolated cardiac myocytes were hypertrophied and exhibited contractile depression with impaired calcium reuptake. Ultrastructural analysis revealed enlarged Golgi stacks and increased transitional vesicles in ventricular myocytes, with increased secretory atrial natriuretic peptide granules and degenerative myelin figures in atrial myocytes; immunogold studies localized Rab1a to these abnormal vesicular structures. A survey of hypertrophy signaling molecules revealed increased protein kinase C (PKC) alpha and delta, and confocal microscopy showed abnormal subcellular distribution of PKCalpha in Rab1a transgenics. These results indicate that increased expression of Rab1 GTPase in myocardium distorts subcellular localization of proteins and is sufficient to cause cardiac hypertrophy and failure.
authors.affiliation: Department of Medicine, University of Cincinnati Medical Center, Cincinnati, Ohio, USA.
authors.forename: G
authors.initials: G
authors.lastname: Wu
authors.forename: M G
authors.initials: MG
authors.lastname: Yussman
authors.forename: T J
authors.initials: TJ
authors.lastname: Barrett
authors.forename: H S
authors.initials: HS
authors.lastname: Hahn
authors.forename: H
authors.initials: H
authors.lastname: Osinska
authors.forename: G M
authors.initials: GM
authors.lastname: Hilliard
authors.forename: X
authors.initials: X
authors.lastname: Wang
authors.forename: T
authors.initials: T
authors.lastname: Toyokawa
authors.forename: A
authors.initials: A
authors.lastname: Yatani
authors.forename: R A
authors.initials: RA
authors.lastname: Lynch
authors.forename: J
authors.initials: J
authors.lastname: Robbins
authors.forename: G W
authors.initials: GW
authors.lastname: Dorn
mesh_terms: D000818:Animals; D015139:Blotting, Southern; D002118:Calcium / Q000378:metabolism; D020746:Calcium Channels, L-Type / Q000378:metabolism; D009202:Cardiomyopathies / Q000201:enzymology* / Q000209:etiology* / Q000473:pathology; D048429:Cell Size / Q000235:genetics; D004195:Disease Models, Animal; D018450:Disease Progression; D015870:Gene Expression; D020730:Guanine Nucleotide Dissociation Inhibitors / Q000378:metabolism; D006801:Humans; D007527:Isoenzymes / Q000378:metabolism; D051379:Mice; D008822:Mice, Transgenic; D009206:Myocardium / Q000201:enzymology* / Q000473:pathology / Q000648:ultrastructure; D015388:Organelles / Q000648:ultrastructure; D018408:Patch-Clamp Techniques; D011493:Protein Kinase C / Q000378:metabolism; D021381:Protein Transport; D012333:RNA, Messenger / Q000378:metabolism; D015398:Signal Transduction; D013045:Species Specificity; D019076:Transgenes; D015854:Up-Regulation / Q000235:genetics; D020691:rab GTP-Binding Proteins / Q000096:biosynthesis* / Q000235:genetics; D020761:rab1 GTP-Binding Proteins / Q000096:biosynthesis / Q000235:genetics
chemical_list: D020746:Calcium Channels, L-Type; D020730:Guanine Nucleotide Dissociation Inhibitors; D007527:Isoenzymes; D012333:RNA, Messenger; D011493:Protein Kinase C; D020691:rab GTP-Binding Proteins; D020761:rab1 GTP-Binding Proteins; D002118:Calcium