Objective
The objective for Aim 1 is to produce the insulin receptor (IR) in lipid bilayers and determine structures of IR in complex with insulin and biased agonists. By solving structures in this physiologically relevant context, we hope to obtain novel insight into the authentic mechanisms of IR signal transduction. The objective for Aim 2 is to use protein design algorithms from the Baker lab at the University of Washington to design potential glucose-binding proteins, which I will then screen and characterize using biochemical and biophysical methodologies. Successful completion of Aim 2 will inform the development of “smart” insulin therapeutics.
Background Rationale
Although insulin therapeutics have improved dramatically over the last century, limitations in insulin safety pose dramatic health concerns. High doses and non-physiological distribution of injected insulin are correlated with an increased risk of cancer due to insulin’s ability to induce mitogenic signaling upon activation of the insulin receptor (IR). New non-insulin IR agonists demonstrate biased activation of metabolic over mitogenic signaling. Unfortunately, structural interrogation of detergent-solubilized IR has failed to show how biased agonists confer preferential metabolic signaling. A second health concern is that insulin-dependent diabetics spend approximately 59% of time outside a normal glycemic range. Hypothetical “smart” insulins, which are reversibly activated in the presence of high blood glucose, could dramatically improve time in range. One promising “smart” insulin design involves conjugating insulin to a glucose binding protein (GBP), whereby glucose binding would cause reversible insulin activation.
Description of Project
Type 1 diabetics require life-long administration of insulin multiple times a day to survive. Unfortunately, therapeutic insulin is coupled to dramatic risks including an increased likelihood of developing cancer with prolonged use and the potential deadly consequences of even slightly miscalculated doses. Improved insulin therapies with reduced risk of cancer and more flexible dosage requirements would dramatically alleviate the constant fight for health and survival faced by all type 1 diabetics. To address these problems, I propose to (Aim 1) investigate the structural rationale for mitogenic insulin signaling with the hope of informing strategies for development of less oncogenic insulin therapies; and (Aim 2) design glucose-binding proteins for future incorporation into glucose-sensitive insulins that are activated only in the presence of high blood glucose concentrations and thus have lenient dosage properties. For Aim 1, I will build upon recent approaches for studying the insulin receptor (IR) in physiologically relevant lipid biolayers to obtain novel insight into its conformations when activated by a range of ligands responsible for either on- or off-target signaling. Insight into these different signaling conformations will hopefully provide a framework for developing less mitogenic insulin therapies. For Aim 2, I will leverage recent advances in artificial intelligence in collaboration with Dr. David Baker to design and test de novo glucose-binding proteins. These proteins could be attached to insulins, allowing them to respond reversibly to changes in blood glucose concentrations. Successful completion of these aims will inform the development of safer insulin therapeutics capable of reducing the risk of diabetes complications and burnout, and increase time spent in a normal glycemic range.
Anticipated Outcome
Successful completion of the work described in Aim 1 of this proposal will result in three high-resolution structures of the full-length insulin receptor in lipid bilayers bound to insulin, a metabolic biased agonist, and a mitogenic biased agonist. Successful completion of Aim 2 will result in design, production, and structure determination of one or more glucose-binding protein(s) with glucose affinities of 5-10 mM.
Relevance to T1D
Insulin is a lifesaving therapeutic for type 1 diabetics who require multiple doses daily for their entire lives. Despite the advances in this transformative drug, there are still numerous limitations and risks associated with insulin therapy. Over time, diabetics often develop insulin resistance and require progressively increasing dosages. Unknown to most diabetics is the growing correlation between prolonged and increasing insulin use and enhanced risk for developing certain cancers. Unfortunately, there are currently no alternative therapies on the market. In addition, type 1 diabetics spend approximately 59% of time outside a normal glycemic range. These departures from euglycemia are uncomfortable, distract from normal tasks, can make it difficult to function, and can be life-threatening and even deadly. Long-term hyperglycemia results in diabetes complications such as heart and kidney disease, neuropathy, blindness, and stroke, to name a few. Since diabetes management is constant and chronic, diabetics also often develop burnout and other psychological diseases including eating disorders and depression. These complications are exacerbated by the difficulty in accurately calculating insulin dosages. Unlike many drugs which can be administered on a regular schedule as a defined dose, diabetics must calculate the amount of insulin needed for each dose based on the timing and composition of their meal. This process is complicated by the numerous and often uncontrollable factors that modulate the body’s sensitivity to insulin including stress, sickness, exercise, and reproductive hormones. Furthermore, insulin has a narrow therapeutic index, meaning that small miscalculations in doses can have catastrophic consequences. Safer insulins with fewer side effects and easier dosing requirements are desperately needed by type 1 diabetics.