Differential involvement of the microtubule cytoskeleton in insulin receptor substrate 1 (IRS-1) and IRS-2 signaling to AKT determines the response to microtubule disruption in breast carcinoma cells.
The insulin receptor substrate (IRS) proteins serve as essential signaling intermediates for the activation of PI3K by both the insulin-like growth factor 1 receptor (IGF-1R) and its close family member, the insulin receptor (IR). Although IRS-1 and IRS-2 share significant homology, they regulate distinct cellular responses downstream of these receptors and play divergent roles in breast cancer. To investigate the mechanism by which signaling through IRS-1 and IRS-2 results in differential outcomes, we assessed the involvement of the microtubule cytoskeleton in IRS-dependent signaling. Treatment with drugs that either stabilize or disrupt microtubules reveal that an intact microtubule cytoskeleton contributes to IRS-2- but not IRS-1-mediated activation of AKT by IGF-1. Proximal IGF-1R signaling events, including IRS tyrosine phosphorylation and recruitment of PI3K, are not inhibited by microtubule disruption, indicating that IRS-2 requires the microtubule cytoskeleton at the level of downstream effector activation. IRS-2 colocalization with tubulin is enhanced upon Taxol-mediated microtubule stabilization, which, together with the signaling data, suggests that the microtubule cytoskeleton may facilitate access of IRS-2 to downstream effectors such as AKT. Of clinical relevance is that our data reveal that expression of IRS-2 sensitizes breast carcinoma cells to apoptosis in response to treatment with microtubule-disrupting drugs, identifying IRS-2 as a potential biomarker for the response of breast cancer patients toVincaalkaloid drug treatment.
From the Department of Molecular, Cell, and Cancer Biology, University of Massachusetts Medical School, Worcester, Massachusetts 01605.
Jose
J
Mercado-Matos
From the Department of Molecular, Cell, and Cancer Biology, University of Massachusetts Medical School, Worcester, Massachusetts 01605.
Jennifer L
JL
Clark
From the Department of Molecular, Cell, and Cancer Biology, University of Massachusetts Medical School, Worcester, Massachusetts 01605.
Andrew J
AJ
Piper
From the Department of Molecular, Cell, and Cancer Biology, University of Massachusetts Medical School, Worcester, Massachusetts 01605.
Jenny
J
Janusis
From the Department of Molecular, Cell, and Cancer Biology, University of Massachusetts Medical School, Worcester, Massachusetts 01605 leslie.shaw@umassmed.edu.
Leslie M
LM
Shaw
D014408:Biomarkers, Tumor / Q000378:metabolism; D001943:Breast Neoplasms / Q000188:drug therapy / Q000378:metabolism*; D002453:Cell Cycle; D045744:Cell Line, Tumor; D003599:Cytoskeleton / Q000378:metabolism; D005260:Female; D006801:Humans; D055504:Insulin Receptor Substrate Proteins / Q000378:metabolism*; D008856:Microscopy, Fluorescence; D008870:Microtubules / Q000187:drug effects / Q000378:metabolism*; D017239:Paclitaxel / Q000737:chemistry; D010766:Phosphorylation; D021381:Protein Transport; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism*; D017526:Receptor, IGF Type 1; D017451:Receptors, Somatomedin / Q000378:metabolism; D015398:Signal Transduction; D014404:Tubulin / Q000737:chemistry; D014443:Tyrosine / Q000737:chemistry
D014408:Biomarkers, Tumor; C000597236:IGF1R protein, human; C526292:IRS1 protein, human; C526297:IRS2 protein, human; D055504:Insulin Receptor Substrate Proteins; D017451:Receptors, Somatomedin; D014404:Tubulin; D014443:Tyrosine; D017526:Receptor, IGF Type 1; C494918:AKT1 protein, human; D051057:Proto-Oncogene Proteins c-akt; D017239:Paclitaxel
Akt PKB; apoptosis; breast cancer; cell signaling; insulin receptor substrate 1 (IRS-1); insulin receptor substrate 2 (IRS-2); microtubule