BACKGROUND: -The primary role of natriuretic peptide receptor 3 (NPR3) or NPR-C is in the clearance of natriuretic peptides that play an important role in modulating intravascular volume and vascular tone. Genetic variation in NPR3 has been associated with variation in blood pressure and obesity. Despite the importance of NPR3, sequence variation in the gene has not been addressed using DNA from different ethnic populations. We set out to identify and functionally characterize genetic variation in NPR3 in 3 ethnic groups. METHODS AND RESULTS: -DNA samples from 96 European-American, 96 African-American, and 96 Han Chinese-American healthy subjects were used to resequence NPR3 exons, splice junctions and flanking regions. We identified 105 polymorphisms, 50 of which were novel, including 8 nonsynonymous (ns) SNPs, 7 were novel. Expression constructs were created for the nsSNP. HEK-293 cells were transfected with constructs for wild type (WT) and variant allozymes; and recombinant proteins were measured by quantitative Western blot analysis. The most significant change in NPR3 protein was observed for the Arg146 variant allozyme, with 20% of WT protein, due primarily to autophagy-dependent degradation. NPR3 structural modeling confirmed that the Arg146 variant protein was not compatible with WT conformation and could result in protein misfolding or instability. CONCLUSIONS: -Multiple novel NPR3 genetic polymorphisms were identified in 3 ethnic groups. The Arg146 allozyme displayed a significant decrease in protein quantity, due to degradation mediated predominantly by autophagy. This genetic variation could have a significant effect on the metabolism of natriuretic peptides with potential clinical implications.
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