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DLC1 activation requires lipid interaction through a polybasic region preceding the RhoGAP domain

Patrik Erlmann1, Simone Schmid, Florian A Horenkamp

  • 1Institute of Cell Biology and Immunology, University of Stuttgart, 70569 Stuttgart, Germany.

Molecular Biology of the Cell
|August 28, 2009
PubMed

Insights

Deleted in Liver Cancer 1 (DLC1), a tumor suppressor, binds phosphatidylinositol-4,5-bisphosphate (PI(4,5)P2) via a novel polybasic region. This interaction enhances DLC1

Area of Science:

  • Molecular biology
  • Cell biology
  • Biochemistry

Background:

  • Deleted in Liver Cancer 1 (DLC1) is a tumor suppressor gene frequently deleted in various cancers.
  • DLC1 functions as a GTPase-activating protein (GAP) for RhoA, RhoB, and RhoC, regulating actin cytoskeleton dynamics, cell migration, and proliferation.

Purpose of the Study:

  • To investigate the regulatory mechanisms of DLC1 activity.
  • To identify novel binding partners and functional domains of DLC1.

Main Methods:

  • In vitro binding assays to assess DLC1 interaction with PI(4,5)P2.
  • Site-directed mutagenesis to create DLC1 mutants lacking a functional polybasic region (PBR).
  • Cell-based assays to evaluate the impact of DLC1 mutations on Rho signaling, cell spreading, migration, and proliferation.

Main Results:

  • DLC1 directly binds to phosphatidylinositol-4,5-bisphosphate (PI(4,5)P2) through a previously unrecognized polybasic region (PBR).
  • PI(4,5)P2-containing membranes significantly stimulate DLC1's GTPase-activating protein (GAP) activity in vitro.
  • A DLC1 mutant lacking an intact PBR exhibited impaired inactivation of Rho signaling and was compromised in suppressing cell spreading, directed migration, and proliferation in living cells.

Conclusions:

  • Phosphatidylinositol-4,5-bisphosphate (PI(4,5)P2) acts as a crucial cofactor for DLC1 regulation in vivo.
  • The polybasic region (PBR) is essential for DLC1's cellular functions, including the regulation of Rho signaling and cell behavior.

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