Altered renal proximal tubular endocytosis and histology in mice lacking myosin-VI.
Myosin VI (Myo6) is an actin-based molecular motor involved in clathrin-mediated endocytosis that is highly expressed in the renal proximal tubule brush border. We investigated the renal physiological consequences of loss of Myo6 function by performing renal clearance and physiological measurements on Myo6 functional null Snell's waltzer (sv/sv) and control heterozygous (+/sv) mice. Sv/sv mice showed reduced body weight and elevated blood pressure compared with controls; no differences were observed for glomerular flow rate, urine volume, blood acid-base parameters, and plasma concentrations and urinary excretions of Na(+) and K(+). To assess the integrity of endocytosis-mediated protein absorption by the kidney, urinary albumin excretion was measured, and the proximal tubular uptake of intravenously injected endocytic marker horseradish peroxidase (HRP) was examined. Albumin excretion was increased nearly 4-fold in sv/sv mice relative to controls. Conversely, HRP uptake was reduced and delayed in proximal tubule cells of the sv/sv kidney observed by electron microscopy at 5 and 30 min after injection. Consistent with impaired endocytosis, we also observed defects indicating alterations along the endocytic pathway in sv/sv proximal tubule cells: (1) decreased membrane association of the clathrin adaptor subunit, adaptin beta, and Disabled-2 (Dab2) after sedimentation of renal homogenates and (2) reduced apical vacuole number. In addition, proximal tubular dilation and fibrosis, likely secondary effects of the loss of Myo6, were observed in sv/sv kidneys. These results indicate that Myo6 plays a key role in endocytosis-mediated protein absorption in the mouse kidney proximal tubule.
Gotoh
Nanami
N
Department of Molecular, Cellular and Developmental Biology, Yale University, New Haven, CT 06520-8103, USA.
Yan
Qingshang
Q
Du
Zhaopeng
Z
Biemesderfer
Daniel
D
Kashgarian
Michael
M
Mooseker
Mark S
MS
Wang
Tong
T
D000199:Actins / Q000378:metabolism; D048868:Adaptor Proteins, Signal Transducing; D033942:Adaptor Proteins, Vesicular Transport / Q000378:metabolism; D000818:Animals; D051017:Apoptosis Regulatory Proteins; D054338:Cell Transdifferentiation; D004705:Endocytosis / Q000502:physiology*; D006735:Horseradish Peroxidase / Q000378:metabolism; D007687:Kidney Tubules, Proximal / Q000473:pathology / Q000502:physiology*; D026561:Low Density Lipoprotein Receptor-Related Protein-2 / Q000378:metabolism; D051379:Mice; D008818:Mice, Neurologic Mutants; D008840:Microfilament Proteins / Q000378:metabolism; D008871:Microvilli / Q000235:genetics / Q000378:metabolism; D018995:Myosin Heavy Chains / Q000172:deficiency*; D033921:Vesicular Transport Proteins / Q000378:metabolism
C558396:Acta2 protein, mouse; D000199:Actins; D048868:Adaptor Proteins, Signal Transducing; D033942:Adaptor Proteins, Vesicular Transport; D051017:Apoptosis Regulatory Proteins; C478773:Dab2 protein, mouse; D026561:Low Density Lipoprotein Receptor-Related Protein-2; C055127:Lrp2 protein, mouse; D008840:Microfilament Proteins; D033921:Vesicular Transport Proteins; C093846:early endosome antigen 1; C089785:myosin VI; C026615:villin; D006735:Horseradish Peroxidase; D018995:Myosin Heavy Chains