A PKCη missense mutation enhances Golgi-localized signaling and is associated with recessively inherited familial Alzheimer’s disease

Abstract

The identification of Alzheimer’s disease (AD)–associated genomic variants has provided powerful insight into disease etiology. Genome-wide association studies (GWASs) of AD have successfully identified previously unidentified targets but have almost exclusively used additive genetic models. Here, we performed a family-based GWAS of a recessive inheritance model using whole-genome sequencing from families affected by AD. We found an association between AD risk and the variant rs7161410, which is located in an intron of the PRKCH gene encoding protein kinase C eta (PKCη). In addition, a rare PRKCH missense mutation, K65R, was in linkage disequilibrium with rs7161410 and was present in homozygous carriers of the rs7161410 risk allele. In vitro analysis revealed that the catalytic rate, lipid dependence, and peptide substrate binding of the purified variant were indistinguishable from those of the wild-type kinase. However, cellular studies revealed that the K65R PKCη variant had reduced cytosolic activity and, instead, enhanced localization and signaling at the Golgi. Moreover, the K65R variant had altered interaction networks in transfected cells, particularly with proteins involved in Golgi processes such as vesicle transport. In human brain tissue, the AD-associated recessive genotype of rs7161410 was associated with increased expression of PRKCH , particularly in the amygdala. This association of aberrant PKCη signaling with AD and the insight into how its function is altered may lead to previously unidentified therapeutic targets for prevention and treatment.

Protein kinase C theta: evolution, regulation, and function

“…The predicted positions of these differences between, but not within, the subfamilies suggest that they may uniquely control the autoinhibited conformation or activation dynamics of the subfamily members. Consistent with this, live cell imaging experiments have revealed that the novel-d isozymes are effectively autoinhibited, whereas the novel-e isozymes are weakly autoinhibited: PKCθ and PKCδ have almost no basal activity in cells [ 11 , 19 ], whereas PKCε and PKCη have high basal activity [ 19 , 20 ]. Thus, novel-d isozymes are under tight second messenger regulation, whereas the novel-e isozymes signal in the absence of second messenger stimulation, likely arising from differences in residues involved in maintaining the autoinhibited conformation.…”

Protein kinase C theta: evolution, regulation, and function

“…The predicted positions of these differences between, but not within, the subfamilies suggest that they may uniquely control the autoinhibited conformation or activation dynamics of the subfamily members. Consistent with this, live cell imaging experiments have revealed that the novel-d isozymes are effectively autoinhibited, whereas the novel-e isozymes are weakly autoinhibited: PKCθ and PKCδ have almost no basal activity in cells [ 11 , 19 ], whereas PKCε and PKCη have high basal activity [ 19 , 20 ]. Thus, novel-d isozymes are under tight second messenger regulation, whereas the novel-e isozymes signal in the absence of second messenger stimulation, likely arising from differences in residues involved in maintaining the autoinhibited conformation.…”

Protein kinase C theta: evolution, regulation, and function

“…The predicted positions of these differences between, but not within, the subfamilies suggest that they may uniquely control the autoinhibited conformation or activation dynamics of the subfamily members. Consistent with this, live cell imaging experiments have revealed that the novel-d isozymes are effectively autoinhibited, whereas the novel-e isozymes are weakly autoinhibited: PKCθ and PKCδ have almost no basal activity in cells [ 11 , 19 ], whereas PKCε and PKCη have high basal activity [ 19 , 20 ]. Thus, novel-d isozymes are under tight second messenger regulation, whereas the novel-e isozymes signal in the absence of second messenger stimulation, likely arising from differences in residues involved in maintaining the autoinhibited conformation.…”

Protein kinase C theta: evolution, regulation, and function

“…The predicted positions of these differences between, but not within, the subfamilies suggest that they may uniquely control the autoinhibited conformation or activation dynamics of the subfamily members. Consistent with this, live cell imaging experiments have revealed that the novel-d isozymes are effectively autoinhibited, whereas the novel-e isozymes are weakly autoinhibited: PKCθ and PKCδ have almost no basal activity in cells [ 11 , 19 ], whereas PKCε and PKCη have high basal activity [ 19 , 20 ]. Thus, novel-d isozymes are under tight second messenger regulation, whereas the novel-e isozymes signal in the absence of second messenger stimulation, likely arising from differences in residues involved in maintaining the autoinhibited conformation.…”