Overexpression of diacylglycerol kinase ? enhances G?q-coupled G protein-coupled receptor signaling.

ABSTRACT: Multiple genome-wide association studies have linked diacylglycerol kinase ? (DGK?) to bipolar disorder (BPD). Moreover, DGK? expression is increased in tissue from patients with BPD. How increased levels of this lipid kinase might affect cellular functions is currently unclear. Here, we overexpressed mouse DGK? in human embryonic kidney 293 cells to examine substrate specificity and signaling downstream of endogenous G protein-coupled receptors (GPCRs). We found that DGK? can phosphorylate diacylglycerol (DAG) with different acyl side chains (8:0, 12:0, 18:1). In addition, overexpression of DGK? enhanced calcium mobilization after stimulating muscarinic receptors with carbachol and after stimulating purinergic receptors with ATP. This effect required DGK? catalytic activity, as assessed using a kinase-dead (G389D) mutant and multiple truncation constructs. DGK? was localized throughout the cytosol and did not translocate to the plasma membrane after stimulation with carbachol. Since protein kinase C (PKC) can be activated by DAG and promotes receptor desensitization, we also examined functional interactions between PKC and DGK?. We found that acute activation of PKC with phorbol 12-myristate 13-acetate shortened carbachol-evoked calcium responses and occluded the effect of overexpressed DGK?. Moreover, inhibition of PKC activity with bisindolylmaleimide I (BIM I) produced the same enhancing effect on carbachol-evoked calcium mobilization as overexpressed DGK?, and overexpression of DGK? produced no additional effect on calcium mobilization in the presence of BIM I. Taken together, our data suggest that DGK? enhances GPCR signaling by reducing PKC activation.

SUBMITTER: Rittiner JE 

PROVIDER: S-EPMC3990018 | biostudies-literature | 2014 May

REPOSITORIES: biostudies-literature