Abstract:
This is a revised grant application entitled “Alterations in Post-Receptor Insulin Signaling in Diabetes and
Insulin Resistance.” Insulin and IGF-1 acting via their cognate receptors (IR and IGF1R) to produce a wide
range of metabolic and growth effects on most cells in the body. Over many years, work from my lab has been
devoted to understanding the intermediate signals in this process and how these may be altered in disease.
Thus, we have characterized extensively the roles of insulin receptor substrate proteins in coupling IR and
IGF1R to downstream effector systems, the important role of PI-3 kinase and Akt in the metabolic actions of
insulin, and effects of MAP/mTOR/S6K kinase pathway in growth promotion. These studies have led to
development of an integrated model of the insulin signaling network in which there are critical nodes of signal
divergence that provide complementary information to different downstream actions of insulin. These critical
nodes also provide important sites of positive and negative regulation that can lead to alterations of insulin
action in disease. Recently, we have begun to dissect the full phosphoproteome downstream IR/IGF1R and,
through this, have identified two new Forkhead transcriptional mediators of insulin/IGF-1 signaling, FoxK1 and
FoxK2. From a disease perspective, we have also shown how different insulin resistant states alter the insulin
signaling network in different tissues. We have also developed iPS cell models to focus on identification of cell
autonomous components of insulin resistance in human disease. Indeed, as shown in our preliminary data,
myoblasts derived from T2D iPSCs demonstrate defects in downstream signaling and metabolic function in
vitro mirroring the defects found in vivo. More importantly, these cells also show dysregulation of a
multidimensional phosphorylation network - both inside and outside the classical insulin signaling cascade. In
this grant, we will focus on two interrelated specific aims: 1) Elucidate the fundamental differences in insulin
signaling in T2D and other insulin resistant states in vitro using targeted and global phosphoproteomics of
human iPS cell-derived myoblasts from normal individuals, T2D patients and non-diabetic individuals with
insulin resistance. We will assess how these changes affect cellular function and participate in insulin
resistance. 2) Define the role of two new downstream transcriptional regulators in insulin action, FoxK1 and
FoxK2. We will identify the genes regulated by FoxK1/2, determine how they complement other transcriptional
regulators in insulin regulation of cellular function, and how they are altered in diabetes. We will also define
FoxK regulated genes using Chip-Seq. Finally, we will create mice with tissue specific deletion of FoxK1,
FoxK2 and selected combinatorial knockouts to define their complementary roles in insulin-regulated gene
expression and insulin action in vivo. Together these studies will lead to a new level of understanding insulin
signaling and its alterations in diabetes, provide deeper understanding of insulin regulation of gene expression
and provide new points for therapy of type 2 diabetes and other insulin resistant disorders.