Wednesday, February 5, 2025
2/5/2025
Abstract Heart failure is a major cause for global mortality/morbidity characterized by the loss of cell surface beta- adrenergic receptor (βAR) which are powerful regulators of cardiac function. Epinephrine/norepinephrine activates βARs leading to cAMP generation and cardiac contraction. Activated βARs are phosphorylated by G- protein coupled receptor kinases resulting in β-arrestin binding and desensitization. Phosphorylated βARs undergo endocytosis, and are dephosphorylated (ie resensitized) in the endosomes by protein phosphatase 2A (PP2A) before being recycled back to the plasma membrane as agonist ready naïve βARs. This reflects a dynamic regulation of βAR function by desensitization (phosphorylation) and resensitization (dephosphorylation). Despite this dynamic regulation, desensitization is well understood, while less is known about resensitization in in heart failure. Our seminal studies identified that phosphoinositide 3-kinase γ (PI3Kγ) phosphorylates an endogenous inhibitor of PP2A (I2PPA) which robustly binds and inhibits PP2A activity thereby, impairing βAR resensitization. In vivo studies using mouse models targeting I2PP2A showed that preservation of resensitization results in maintenance of βAR function conferring cardiac protection. Consistently, βAR resensitization is inhibited in end-stage human heart failure which is characterized by significant loss in PP2A activity compared to non-failing hearts. These findings lay the rationale for the scientific premise that therapeutic approaches to unlock the inhibition of PP2A activity leading to preservation of βAR resensitization would ameliorate cardiac dysfunction. We came across a small molecule (TGI1002, TGI) in cancer space that maintains PP2A function by targeting I2PP2A unlocking PP2A inhibition. As mechanistic basis for I2PP2A targeting by TGI is not known, in silico docking, cellular and in vitro studies were performed which showed that TGI impaired I2PP2A binding to PP2A resulting in sustained βAR-associated PP2A activity and preserved βAR resensitization. However, TGI generates baseline cAMP, which is thought to be cardiotoxic. In recognition, our initial structure-design activity studies led to analog like CCF002, which though not optimal has reduced baseline cAMP, improved in vitro activity over TGI and importantly, mitigated cardiac dysfunction post-heart failure administration. Thus, the R61 phase is focused on understanding the pharmacophore to generate molecules that have minimal baseline cAMP, higher in vitro efficacies through optimizing modifications on CCF002. This could lead to identification of 1-3 candidates with drug-like properties with higher efficacies and bioavailability preserving βAR resensitization. The R33 phase is designed to comprehensively assess in vitro toxicity, off-target effects and efficacy on a second hypertension-based model of heart failure in acknowledgement of the heart failure etiology. The studies outlined in the grant application would allow us to translate early stage discovery to identify and characterize potential therapeutic molecules for heart failure congruent with the Catalyze funding opportunity announcement (FOA).
HHS’ Tracking Accountability in Government Grants System (TAGGS) website provides access to detailed descriptions of grants, loans, aggregated direct payments and other types of financial assistance awarded by the HHS Operating Divisions (OPDIVs) and the Office of the Secretary Staff Divisions (STAFFDIVs).