Negative regulators of insulin signaling revealed in a genome-wide functional screen.
BACKGROUND
Type 2 diabetes develops due to a combination of insulin resistance and beta-cell failure and current therapeutics aim at both of these underlying causes. Several negative regulators of insulin signaling are known and are the subject of drug discovery efforts. We sought to identify novel contributors to insulin resistance and hence potentially novel targets for therapeutic intervention.


METHODS
An arrayed cDNA library encoding 18,441 human transcripts was screened for inhibitors of insulin signaling and revealed known inhibitors and numerous potential novel regulators. The novel hits included proteins of various functional classes such as kinases, phosphatases, transcription factors, and GTPase associated proteins. A series of secondary assays confirmed the relevance of the primary screen hits to insulin signaling and provided further insight into their modes of action.


CONCLUSIONS
Among the novel hits was PALD (KIAA1274, paladin), a previously uncharacterized protein that when overexpressed led to inhibition of insulin's ability to down regulate a FOXO1A-driven reporter gene, reduced upstream insulin-stimulated AKT phosphorylation, and decreased insulin receptor (IR) abundance. Conversely, knockdown of PALD gene expression resulted in increased IR abundance, enhanced insulin-stimulated AKT phosphorylation, and an improvement in insulin's ability to suppress FOXO1A-driven reporter gene activity. The present data demonstrate that the application of arrayed genome-wide screening technologies to insulin signaling is fruitful and is likely to reveal novel drug targets for insulin resistance and the metabolic syndrome.
Huang
Shih-Min A
SM
Genomics Institute of the Novartis Research Foundation, San Diego, California, United States of America.
Hancock
Michael K
MK
Pitman
Jeffrey L
JL
Orth
Anthony P
AP
Gekakis
Nicholas
N
D000818:Animals; D016466:CHO Cells; D006224:Cricetinae; D003412:Cricetulus; D003924:Diabetes Mellitus, Type 2 / Q000378:metabolism*; D000071161:Forkhead Box Protein O1; D051858:Forkhead Transcription Factors / Q000378:metabolism; D005786:Gene Expression Regulation; D015723:Gene Library; D017930:Genes, Reporter; D006801:Humans; D007328:Insulin / Q000378:metabolism*; D007333:Insulin Resistance; D050417:Insulin-Secreting Cells / Q000378:metabolism*; D010749:Phosphoprotein Phosphatases; D010766:Phosphorylation; D011506:Proteins / Q000378:metabolism / Q000502:physiology; D015398:Signal Transduction
C085126:FOXO1 protein, human; D000071161:Forkhead Box Protein O1; D051858:Forkhead Transcription Factors; D007328:Insulin; D011506:Proteins; C546583:PALD1 protein, human; D010749:Phosphoprotein Phosphatases