Chan Research

Targeting Akt Kinase and PKA Dephosphorylation Mechanisms to Heal Skin, Lung & Radiation Wounds

My laboratory focuses on the understanding the mechanisms that regulate Akt kinase and Protein Kinase A (PKA). Our studies of an inherited mutation for Akt2 protein kinase that causes insulin resistance led to the discovery of a series of molecular switches that regulate Akt dephosphorylation. The implications and importance of this work, as applicable to general protein kinases, was published in PNAS and discussed in perspective articles.

Molecular Mechanisms and Signaling Regulation of Phosphatase Sensitivity in Akt kinase and in Protein Kinase A

Based on an inherited mutation in the Akt2 gene that causes insulin resistance in the cardiovascular system, we discovered a series of molecular switches that regulate Akt dephosphorylation. The implications of this work are applicable to other protein kinases, including Protein Kinase A. We are dissecting the biochemical, biophysical and physiological mechanisms of this molecular switch in Akt kinase and in Protein Kinase A and the effects of regulating this switch in airway cells, skin cells and cardiomyocytes.  

Akt Activator Drug Discovery and Development

The phosphoinositol lipid-derived second messenger, PtdIns-3,4,5-P3, enables the activation of Akt kinase (also known as PKB). Activation of Akt kinase has been implicated in the regulation of a diverse array of cellular functions such as anti-apoptosis, metabolism, proliferation and differentiation and governs cell survival.

Based on our discovery of a series of molecular switches that regulate Akt dephosphorylation, we identified small molecules targeting this switch mechanism to enable Akt kinase activation. These novel drugs have immediate utility towards protecting the survival of cells during injurious insults. In collaboration with a drug design and synthesis team, we are employing cellular, genetic, pharmacological, biophysical assays to advance our drug discovery efforts. We are testing our lead Akt activators in relevant cell culture and animal models to protect acute lung injury, skin wound injury and radiation-induced cardiac injury.  

Novel Protein Kinase A Signaling Pathways Associated with Lung Diseases

We recently dissected the biochemical, biophysical and physiological mechanisms that regulate phosphatase sensitivity in Protein Kinase A (PKA) using airway smooth muscle cells (JBC, 2020). PKA signals affecting lung airway function are regulated through complementary tyrosine kinase receptor and G-protein coupled receptor (GPCR) signals. We are studying changes in compartmentalized GPCR signaling (focusing on b2AR or EP receptor) and/or receptor complementation signaling. These signals alter PKA phosphorylation/dephosphorylation under conditions of inflammation/oxidative stress. Our studies allow us to design and validate small molecules targeting specific molecular motifs to affect physio-biochemical changes. Our work has uncovered novel mechanisms that mediate compartmentalized signaling and promote the discovery of new drugs for asthma therapy.

Leber congenital amaurosis 8 (LCA8) is the most severe, non-treatable, early-onset blinding disease that is caused by recessive mutations in Crumbs homolog 1 (Crb1) gene. About 20% of children attending schools for the blind around world are affected by LCA. Recently we generated mouse model of LCA8 by conditional gene knock-out of Crb1 and its paralog, Crb2, which recapitulated crucial features of human LCA8 pathology. These include temporarily thickened, delaminated retina and early-onset visual loss at the eye opening stage. Our current research focuses on characterizing cellular and molecular defects in the mutant retinal progenitor cells, which undergo defective interkinetic nuclear migration that may alter cellular processes involved in cell proliferation, growth, apico-basal polarity and actomyosin cytoskeleton regulation. In addition, we investigate the outcome of the perturbed intracellular signaling cascades that are mediated by Hippo-Yap, TSC1/2-mTOR and RhoA-ROCK pathways. Our goal is to delineate retinal progenitor-specific cellular and molecular mechanisms underlying LCA8 pathologies using genetic and pharmacological approaches.