The PRKACA gene encodes for the catalytic subunit of protein kinase A (PKA-C). Recent ge- nomic efforts have identified several single-site mutations, insertions, and aberrant fusions directly linked to endocrine diseases. Specifically, a few somatic or germline mutations/insertions have been linked to adenoma-associated Cushing’s syndrome and its associated cardiac myxomas. Additionally, two chimeras are drivers for fibrolamellar hepatocellular carcinoma (FLHCC) and intraductal oncocytic papillary neoplasms (IOPNs) of the pancreas and bile ducts. Recent litera- ture and our preliminary studies suggest dysfunctional spatiotemporal regulation and loss in substrate specificity of PKA-C may represent common traits for the progression of these dis- eases. However, there are no conclusive molecular mechanisms underlying the progression of these diseases. We hypothesize that these PKA-C variants disrupt the allosteric cooperativity that drives the assembly/disassembly of the regulatory complexes, unleashing active PKA-C. We pro- pose to use state-of-the-art liquid-state NMR techniques coupled with biophysical and biochemi- cal approaches to characterize the interactions between PKA-C and its regulatory subunits and the endogenous regulator PKI. We will assess how mutations, insertions, and fusion chimeras of PKA-C disrupt intra- and inter-molecular allostery, leading to aberrant regulation and disease. Understanding the regulatory mechanism of PKA help determine the molecular etiology of these diseases and aid in the future design of strategies to precisely control the aberrant activity of kinases.