title: Isoform-specific interactions between meprin metalloproteases and the catalytic subunit of protein kinase A: significance in acute and chronic kidney injury.
abstract: Meprin metalloproteases are abundantly expressed in the brush-border membranes of kidney proximal tubules. Meprins are implicated in ischemia-reperfusion (IR)-induced renal injury and diabetic nephropathy. The protein kinase A (PKA) signaling pathway modulates extracellular matrix metabolism in diabetic kidneys. The present study evaluated isoform-specific interactions between the catalytic subunit of PKA (PKA C) and meprins. To this end, cytosolic-enriched kidney proteins from meprin αβ double knockout mice, and purified forms of recombinant mouse PKA Cα, Cβ1, and Cβ2, were incubated with activated forms of either homomeric meprin A or meprin B. The cleaved protein products were subjected to SDS-PAGE and analyzed by Coomassie staining and Western blot analysis. While meprin A only cleaved PKA Cβ1, meprin B cleaved all three PKA C isoforms. Analysis of the proteolytic fragments by mass spectrometry revealed that meprin A and B cleave the PKA C isoforms at defined sites, resulting in unique cleavage products. Michaelis-Menten enzyme kinetics demonstrated that meprin B-mediated cleavage of PKA Cα occurs at a rate consistent with that of other physiologically relevant meprin substrates. Meprin cleavage decreased the kinase activity of PKA Cα, Cβ1, and Cβ2. PKA C levels were higher in diabetic kidneys, with evidence of in vivo fragmentation in wild-type diabetic kidneys. Confocal microscopy showed localization of meprin A in the glomeruli of diabetic kidneys. At 3 h post-IR, PKA C levels in proximal tubules decreased compared with distal tubules, which lack meprins. These data suggest that meprins may impact kidney injury, in part, via modulation of PKA signaling pathways.
authors.affiliation: Department of Biology, North Carolina A&T State University, Greensboro, North Carolina;
authors.forename: Jean-Marie V
authors.initials: JM
authors.lastname: Niyitegeka
authors.affiliation: Department of Pharmacology, University of California, San Diego, California; and.
authors.forename: Adam C
authors.initials: AC
authors.lastname: Bastidas
authors.affiliation: Department of Biology, North Carolina A&T State University, Greensboro, North Carolina;
authors.forename: Robert H
authors.initials: RH
authors.lastname: Newman
authors.affiliation: Department of Pharmacology, University of California, San Diego, California; and Howard Hughes Medical Institute, University of California, San Diego, California.
authors.forename: Susan S
authors.initials: SS
authors.lastname: Taylor
authors.affiliation: Department of Biology, North Carolina A&T State University, Greensboro, North Carolina; eongeri@ncat.edu.
authors.forename: Elimelda Moige
authors.initials: EM
authors.lastname: Ongeri
mesh_terms: D058186:Acute Kidney Injury / Q000201:enzymology*; D000595:Amino Acid Sequence; D000818:Animals; D054751:Cyclic AMP-Dependent Protein Kinase Catalytic Subunits / Q000378:metabolism*; D003928:Diabetic Nephropathies / Q000201:enzymology; D057809:HEK293 Cells; D006801:Humans; D007527:Isoenzymes / Q000378:metabolism; D007678:Kidney Glomerulus / Q000201:enzymology; D008666:Metalloendopeptidases / Q000378:metabolism*; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008969:Molecular Sequence Data; D051381:Rats; D051436:Renal Insufficiency, Chronic / Q000201:enzymology*; D015427:Reperfusion Injury / Q000201:enzymology
chemical_list: D007527:Isoenzymes; D054751:Cyclic AMP-Dependent Protein Kinase Catalytic Subunits; D008666:Metalloendopeptidases; C053833:meprin A; C095663:meprin B
keywords: diabetic nephropathy; enzyme processing; ischemia-reperfusion; isoforms; meprin metalloproteases; protein kinase A (PKA)