Project Abstract: Hugh Nam, PhD

Neurogranin Regulation of Nitric Oxide Signaling in Cardiovascular Disease

Schizophrenia patients have a greater rate of premature death from cardiovascular disease compared with the
general population. Although the higher incidence of cardiovascular disease in schizophrenia patients is due to
increased cardiovascular disease risk factors, new evidence suggests genetic susceptibility in this patient
group may account for the greater risk of cardiovascular disease. Therefore, it is pertinent to identify
mechanistic relationships that could act as a pathophysiological link between schizophrenia and cardiovascular
disease.

Human clinical studies highlighted the link between a genetic variant of Neurogranin (Ng, 7.6 kDa), a
calmodulin (CaM)-binding protein, thought to be exclusively expressed in the brain, and a risk of developing
schizophrenia. Interestingly, we recently discovered that deletion of Ng in mice also resulted in significant
cardiac dysfunction; it was associated with decreased ejection fraction and fractional shortening as well as
perivascular fibrosis. Ng –/– mice also show decreased plasma nitric oxide (NO) levels, indicative of endothelial
cell dysfunction, similar to the endothelial NO synthase (eNOS) dysfunction observed in schizophrenic
patients. Our preliminary studies also demonstrated that Ng is highly expressed in the endothelium and
significantly up-regulated in response to laminar flow, a known inducer of NO production. Thus, we
hypothesize that Ng mediates Ca2+-dependent eNOS activity in the endothelium and that defects in Ng
signaling increases vascular resistance resulting in cardiac fibrosis, hypertrophy, and eventually cardiac failure.

To test this hypothesis, AIM1 will determine the mechanistic role of Ng in eNOS signaling using in vitro
approaches. We will test whether altered Ng expression using knockout (Ng siRNA and Ng CRISPR/Cas9
knockout) and overexpression (Lentivirus-oNg and Lentivirus-dnNg) affect eNOS expression and the sensitivity
of eNOS to inflammation. AIM2 will also determine the effect of Ng deletion on cardiovascular function in mice.
We will conduct flow-mediated vasodilation and angiotensin II infusion to test the susceptibility of Ng-mediated
vascular resistance and cardiac failure. The results of these aims will discover a novel Ng-eNOS mechanism in
the endothelium that contributes to cardiac dysfunction. Moreover, these results will contribute to our goal of
establishing clinical interventions between cardiovascular disease and schizophrenia and to positively impact
treatment strategies for cardiovascular disease.

The Center for Redox Biology and Cardiovascular Disease is supported by the National Institute of General Medical Sciences of the National Institutes of Health under Award Number P20GM121307.