Amino acid variant in the kinase binding domain of dual-specific A kinase-anchoring protein 2: A disease susceptibility polymorphism

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Abstract
The focus of human genetics in recent years has shifted toward identifying genes that are involved in the development of common diseases such as cancer, diabetes, cardiovascular diseases, and Alzheimer's disease. Because many complex diseases are late-onset, the frequencies of disease susceptibility alleles are expected to decrease in the healthy elderly individuals of the population at large because of their contribution to disease morbidity and/or mortality. To test this assumption, we compared allele frequencies of 6,500 single-nucleotide polymorphisms (SNPs) located in ≈5,000 genes between DNA pools of age-stratified healthy, European-American individuals. A SNP that results in an amino acid change from Ile to Val in the dual-specific A kinase-anchoring protein 2 (d-AKAP2) gene, showed the strongest correlation with age. Subsequent analysis of an independent sample indicated that the Val variant was associated with a statistically significant decrease in the length of the electrocardiogram PR interval. The Ile/Val SNP is located in the A-kinase-binding domain. An in vitro binding assay revealed that the Ile variant bound ≈3-fold weaker to the protein kinase A (PKA)-RIα isoform than the Val variant. This decreased affinity resulted in alterations in the subcellular distribution of the recombinantly expressed PKA-RIα isoform. Our study suggests that alterations in PKA-RIα subcellular localization caused by variation in d-AKAP2 may have a negative health prognosis in the aging population, which may be related to cardiac dysfunction. Age-stratified samples appear to be useful for screening SNPs to identify functional gene variants that have an impact on health.