PTP1B-dependent insulin receptor phosphorylation/residency in the endocytic recycling compartment of CHO-IR cells.

Insulin binds to the alpha subunit of the insulin receptor (IR) on the cell surface. The insulin-IR complex is subsequently internalized and trafficked within the cell. Endocytosed receptors, devoid of insulin, recycle back to the plasma membrane through the endocytic recycling compartment (ERC). Using a high content screening system, we investigate the intracellular trafficking of the IR and its phosphorylation state, within the ERC, in response to protein tyrosine phosphatase-1B (PTP1B) inhibition. Insulin stimulates, in a time- and dose-dependent manner, the accumulation of phosphorylated IR (pY(1158,1162,1163 IR) in the ERC of CHO-IR cells. Treatment of CHO-IR cells with PTP1B-specific inhibitors or siRNA leads to dose-dependent increases in IR residency and phosphorylation within the ERC. The results also demonstrate that PTP1B redistributes within CHO-IR cells upon insulin challenge. The established system will allow for efficient screening of candidate inhibitors for the modulation of PTP1B activity.