DHHC5 REGULATES BETA-ADRENERGIC SIGNALING IN THE HEART THROUGH PALMITOYLATION OF G ALPHA PROTEINS
Author ORCID Identifier
Date of Graduation
Biochemistry and Molecular Biology
Doctor of Philosophy (PhD)
Ambro van Hoof
S-palmitoylation is a reversible posttranslational modification that plays an important role in regulating protein localization, trafficking, and stability. Recent studies have shown that some proteins undergo extremely rapid palmitoylation/depalmitoylation cycles after cellular stimulation supporting a direct signaling role for this posttranslational modification. The work in this dissertation investigated whether β-adrenergic stimulation led to stimulus-dependent palmitoylation of downstream signaling proteins in immortalized and primary cell models. I found that β-adrenergic stimulation led to rapidly increased Gαs and Gαi palmitoylation only in primary cardiomyocytes. The kinetics of palmitoylation was temporally consistent with the downstream production of cAMP and contractile responses. I identified the plasma membrane-localized palmitoyl acyltransferase DHHC5 as an important mediator of the stimulus-dependent palmitoylation in cardiomyocytes. Knockdown of DHHC5 showed that this enzyme is necessary for palmitoylation of Gαs, Gαi, and functional responses downstream of β-adrenergic stimulation. A palmitoylation assay with purified components revealed that Gαs and Gαi are direct substrates of DHHC5. Finally, we provided evidence that the C-terminal tail of DHHC5 can be palmitoylated in response to stimulation and such modification is important for its dynamic localization in the plasma membrane. My results reveal that DHHC5 is a central regulator of signaling downstream of β-adrenergic receptors in cardiomyocytes.
Palmitoylation, DHHC proteins, Beta-adrenergic signaling