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A conserved role of IQGAP1 in regulating TOR complex 1
Yemsrach K Tekletsadik1, Robert Sonn, Mahasin A Osman
1Institute for Biotechnology and Life Sciences, Cornell University, Ithaca, NY 14853-2703, USA.
Journal of Cell Science
|February 14, 2012
Summary
IQGAP1 regulates cell growth and division by influencing the mTORC1 pathway. Dysregulation of IQGAP1 is linked to tumorigenesis and other diseases, offering potential therapeutic targets.
Area of Science:
- Molecular Biology
- Cell Biology
- Cancer Research
Background:
- Cellular homeostasis, critical for health, is disrupted in diseases like cancer and diabetes.
- IQGAP1, a CDC42 regulator, is implicated in cell proliferation but its role in tumorigenesis is unclear.
- The mTOR pathway controls cell growth and is often activated in cancers, yet remains a challenging therapeutic target due to incomplete mechanistic understanding.
Purpose of the Study:
- To investigate the role of IQGAP1 in regulating the mTOR complex 1 (mTORC1) negative feedback loop (NFL) controlling cell growth.
- To elucidate the molecular mechanisms by which IQGAP1 couples cell growth and division.
- To explore IQGAP1's potential involvement in tumorigenesis and its implications for cancer therapeutics.
Main Methods:
- Utilized complementary studies in yeast and mammalian cells.
- Employed two-hybrid screens to identify binding partners of IQGAP1.
- Analyzed protein phosphorylation and cellular phenotypes in response to epidermal growth factor (EGF) and specific IQGAP1 constructs.
Main Results:
- Identified yeast Tco89p as an Iqg1p-binding partner, linking cell growth and division.
- Demonstrated that mammalian IQGAP1 binds mTORC1 and Akt1.
- Observed that cells expressing an IQGAP1 binding region showed altered ERK1/2 and GSK3α/β activity, with increased Akt1 S473-P but decreased S6K1 T389-P, inducing transformed phenotypes.
Conclusions:
- IQGAP1 acts as a rheostat, regulating cell homeostasis by influencing the mTORC1-S6K1→Akt1 NFL and coupling cell growth with division.
- IQGAP1's dysregulation contributes to tumorigenesis and other diseases.
- Findings suggest IQGAP1 as a potential target for novel anticancer therapeutics.
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