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J Clin Invest. 2018 Aug 1;128(8):3445-3459. doi: 10.1172/JCI99507. Epub 2018 Jul 9.

CaMK4 compromises podocyte function in autoimmune and nonautoimmune kidney disease.

Author information

1
Department of Medicine, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts, USA.
2
Histopathology Core, National Eye Institute, NIH, Bethesda, Maryland, USA.
3
Department of Immunology and Rheumatology, Division of Advanced Preventive Medical Sciences, Nagasaki University Graduate School of Biomedical Sciences, Nagasaki, Japan.
4
Department of Nephrology, Nagasaki University Hospital, Nagasaki, Japan.
5
Department of Nephrology, Nagoya University Graduate School of Medicine, Nagoya, Japan.
6
Department of Biomedical Engineering, Yale University and Yale University School of Medicine, New Haven, Connecticut, USA.
7
Department of Biomedical Engineering, Department of Chemical and Environmental Engineering, Department of Immunobiology, Yale University and Yale University School of Medicine, New Haven, Connecticut, USA.

Abstract

Podocyte malfunction occurs in autoimmune and nonautoimmune kidney disease. Calcium signaling is essential for podocyte injury, but the role of Ca2+/calmodulin-dependent kinase (CaMK) signaling in podocytes has not been fully explored. We report that podocytes from patients with lupus nephritis and focal segmental glomerulosclerosis and lupus-prone and lipopolysaccharide- or adriamycin-treated mice display increased expression of CaMK IV (CaMK4), but not CaMK2. Mechanistically, CaMK4 modulated podocyte motility by altering the expression of the GTPases Rac1 and RhoA and suppressed the expression of nephrin, synaptopodin, and actin fibers in podocytes. In addition, it phosphorylated the scaffold protein 14-3-3β, which resulted in the release and degradation of synaptopodin. Targeted delivery of a CaMK4 inhibitor to podocytes preserved their ultrastructure, averted immune complex deposition and crescent formation, and suppressed proteinuria in lupus-prone mice and proteinuria in mice exposed to lipopolysaccharide-induced podocyte injury by preserving nephrin/synaptopodin expression. In animals exposed to adriamycin, podocyte-specific delivery of a CaMK4 inhibitor prevented and reversed podocyte injury and renal disease. We conclude that CaMK4 is pivotal in immune and nonimmune podocyte injury and that its targeted cell-specific inhibition preserves podocyte structure and function and should have therapeutic value in lupus nephritis and podocytopathies, including focal segmental glomerulosclerosis.

KEYWORDS:

Autoimmunity; Calcium signaling; Calmodulin; Lupus; Nephrology

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