Novel Therapies for Congenital Hyperinsulinism

PROJECT SUMMARY Congenital hyperinsulinism (CHI) is an infantile/childhood disorder causing life-threatening hypoglycemia, brain damage, and developmental defects due to persistent over-secretion of insulin by pancreatic β-cells. CHI most commonly results from loss-of-function mutations in the pancreatic KATP potassium channel subunits, Kir6.2 and SUR1, encoded by KCNJ11 and ABCC8, respectively. KATP channels homeostatically couple insulin secretion and plasma blood glucose. Loss of KATP activity can result from loss of expression and/or loss of channel gating function. A subset of CHI patients retains sufficient residual KATP function to be treated successfully with a KATP channel opener, diazoxide. However, diazoxide is ineffective in numerous CHI patients who harbor mutations that impair KATP expression at the β-cell surface. These include missense mutations that disrupt folding, assembly, and/or trafficking of the channel to the plasma membrane, and nonsense mutations that introduce premature termination codons (PTCs) and prevent translation of full-length functional proteins. To avoid brain damage from severe hypoglycemia, patients carrying such mutations may require total pancreatectomy, which causes life-long insulin-dependent diabetes and digestive complications. Current gene replacement therapy methods using adeno-associated virus vectors are not suitable for the large SUR1 subunit, which harbors the great majority of KATP trafficking/nonsense mutations. Thus, there is a critical need for novel therapeutic strategies for diazoxide-unresponsive KATP-CHI. In this R21 application, we address this unmet challenge by exploring novel therapeutic concepts. Specifically, we hypothesize that (1) pharmacological correctors can rescue trafficking-impaired KATP channel mutants to restore insulin secretion regulation, and (2) Anti-Codon Engineered (ACE)-tRNAs can suppress PTCs to restore expression and function of KATP channels bearing nonsense mutations. We propose to establish cell and animal models of CHI-KATP mutations and conduct pilot studies needed to advance these new therapeutic concepts in two independent Aims. In Aim 1, we will generate and characterize human β-cell line and mouse models of CHI-KATP trafficking mutations and test the ability of pharmacological correctors to restore channel expression and function as well as normalize insulin secretion. In Aim 2, we will conduct a high-throughput screening to identify SUR1-PTCs amenable to ACE-tRNA rescue in a heterologous expression system, followed by generation of human β-cell lines harboring such mutations to evaluate insulin secretion correction by ACE-tRNAs. The proposal’s premise is built on a rigorous review of the literature and strong preliminary and published data from the investigative team members who have complementary expertise. The proposal is innovative as it will generate new tools and knowledge to advance new therapeutic concepts for CHI. Successful outcomes may transform the landscape of CHI clinical therapy and potentially impact discovery of therapeutics for other congenital diseases caused by similar molecular def ects.