Abstract
Phosphoinositide 3-kinases (PI3-Ks) are an important emerging class of drug targets, but the unique roles of PI3-K isoforms remain poorly defined. We describe here an approach to pharmacologically interrogate the PI3-K family. A chemically diverse panel of PI3-K inhibitors was synthesized, and their target selectivity was biochemically enumerated, revealing cryptic homologies across targets and chemotypes. Crystal structures of three inhibitors bound to p110gamma identify a conformationally mobile region that is uniquely exploited by selective compounds. This chemical array was then used to define the PI3-K isoforms required for insulin signaling. We find that p110alpha is the primary insulin-responsive PI3-K in cultured cells, whereas p110beta is dispensable but sets a phenotypic threshold for p110alpha activity. Compounds targeting p110alpha block the acute effects of insulin treatment in vivo, whereas a p110beta inhibitor has no effect. These results illustrate systematic target validation using a matrix of inhibitors that span a protein family.
Publication types
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Research Support, N.I.H., Extramural
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Research Support, N.I.H., Intramural
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Research Support, Non-U.S. Gov't
MeSH terms
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Adipose Tissue / cytology
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Animals
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Binding Sites
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Class I Phosphatidylinositol 3-Kinases
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Crystallography, X-Ray
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Enzyme Inhibitors / chemistry*
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Enzyme Inhibitors / metabolism
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Female
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Glucose / metabolism
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Humans
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Insulin / metabolism*
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Insulin Receptor Substrate Proteins
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Isoenzymes / antagonists & inhibitors*
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Isoenzymes / chemistry
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Isoenzymes / genetics
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Isoenzymes / metabolism*
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Mice
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Models, Molecular
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Molecular Structure
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Muscle Fibers, Skeletal / metabolism
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Phosphatidylinositol 3-Kinases / chemistry
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Phosphatidylinositol 3-Kinases / genetics
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Phosphatidylinositol 3-Kinases / metabolism*
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Phosphoinositide-3 Kinase Inhibitors*
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Phosphoproteins / metabolism
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Signal Transduction / physiology*
Substances
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Enzyme Inhibitors
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IRS1 protein, human
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Insulin
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Insulin Receptor Substrate Proteins
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Irs1 protein, mouse
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Isoenzymes
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Phosphoinositide-3 Kinase Inhibitors
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Phosphoproteins
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1-phosphatidylinositol 3-kinase p110 subunit, mouse
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Class I Phosphatidylinositol 3-Kinases
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Glucose