Isoform‐specific interactions between meprin metalloproteases and the catalytic subunit of protein kinase A (690.13)

Abstract

Meprin metalloproteases are abundantly expressed in the brush border membranes of kidney proximal tubules. Meprins are also expressed in podocytes, skin, and leukocytes. Meprins have been implicated in the pathology of acute and chronic kidney injury. To understand how meprins impact kidney disease, it is important to characterize interactions between meprins and their substrates. This study evaluated isoform‐specific interactions between the catalytic subunit of protein kinase A (PKA C) and meprins. Kidney proteins from meprin αβ double knockout mice, as well as purified recombinant mouse PKA Cα, Cβ1, and Cβ2, were incubated with activated forms of either meprin A (α‐α) or meprin B (β‐β). Cleavage products were analyzed by Coomassie staining or Western blot analysis. To identify meprin cleavage sites on PKA C isoforms, full length PKA C and meprin cleaved fragments were trypsin digested, separated by C18 nanoflow liquid chromatography‐MALDI, and analyzed by ProteinPilot. To characterize the kinetics of meprin B cleavage of PKA Cα, the Km and kcat were determined using Michaelis‐Menten enzyme kinetics. Meprin A only cleaved PKA Cβ1 while meprin B cleaved all three PKA C isoforms. Moreover, meprin cleavage of PKA Cα and Cβ2 significantly decreased their kinase activity, suggesting that the impact of meprins on kidney injury may be due, in part, to modulation of PKA signaling pathways.Grant Funding Source: Supported by NIH grants SC3GM102049, GM19301, GM19301, F31GM099415, and DK19691