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An activated Ras protein alters cell adhesion by dephosphorylating Dictyostelium DdCAD-1

David M Secko1, Chi-Hung Siu2, George B Spiegelman1

  • 1Department of Microbiology and Immunology, University of British Columbia, Life Sciences Centre, 2350 Health Sciences Mall, Vancouver, British Columbia V6T 1Z4, Canada.

Microbiology (Reading, England)
|April 20, 2006
PubMed

Insights

RasG signaling influences Dictyostelium development by regulating cell adhesion molecule DdCAD-1. It affects DdCAD-1 phosphorylation and expression, impacting cell cohesion during early development.

Area of Science:

  • Cellular and Molecular Biology
  • Developmental Biology
  • Biochemistry

Background:

  • RasG-regulated signal transduction is crucial for growth-specific processes and Dictyostelium discoideum early development.
  • The cell adhesion molecule DdCAD-1's phosphorylation is affected by RasG signaling.
  • Previous studies identified DdCAD-1 as a potential component in Ras-mediated signaling pathways.

Purpose of the Study:

  • To investigate the molecular mechanisms of Ras-mediated signaling in Dictyostelium.
  • To elucidate the role of DdCAD-1 in RasG-dependent processes.
  • To understand how RasG affects cell-cell adhesion and DdCAD-1 regulation.

Main Methods:

  • Characterization of a cadA null strain to confirm DdCAD-1 presence.
  • Analysis of cells expressing constitutively active RasG (RasG(G12T)) for changes in cell cohesion and DdCAD-1 phosphorylation.
  • Investigation of DdCAD-1 localization and phosphorylation during Dictyostelium aggregation.
  • Assessment of DdCAD-1 protein levels in a rasG null cell line.

Main Results:

  • A cadA null strain confirmed the absence of DdCAD-1 phosphoproteins.
  • RasG(G12T) expression led to increased cell-cell cohesion and reduced DdCAD-1 phosphorylation.
  • Increased cell cohesion was dependent on DdCAD-1 and associated with its enhanced cell surface localization.
  • DdCAD-1 phosphorylation decreased during Dictyostelium aggregation.
  • RasG null cells showed substantially reduced levels of DdCAD-1 protein.

Conclusions:

  • Protein phosphorylation plays a role in regulating DdCAD-1-mediated cell adhesion during Dictyostelium early development.
  • RasG influences both the expression and dephosphorylation of DdCAD-1.
  • These findings reveal a novel regulatory link between RasG signaling and cell adhesion molecule function in Dictyostelium development.

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