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A mutation that separates the RasG signals that regulate development and cytoskeletal function in Dictyostelium
T Zhang1, P J Rebstein, M Khosla
1Department of Microbiology and Immunology, Department of Medical Genetics, University of British Columbia, 6174 University Boulevard, Vancouver, British Columbia, V6T 1Z3, Canada.
Experimental Cell Research
|March 6, 1999
Summary
Activated RasG in Dictyostelium discoideum alters cell shape and F-actin distribution, impacting cytoskeletal rearrangement and development. Signaling through RasG
Area of Science:
- Cell Biology
- Molecular Biology
- Developmental Biology
Background:
- Ras proteins are key regulators of cellular processes, including cytoskeletal dynamics and development.
- Previous work indicated RasG regulates starvation-induced aggregation in Dictyostelium discoideum.
- Understanding RasG's downstream effectors is crucial for elucidating its regulatory roles.
Purpose of the Study:
- To investigate the role of RasG in regulating cytoskeletal rearrangement and cell morphology in Dictyostelium discoideum.
- To determine if RasG's effects on morphology and development are mediated through a single downstream effector.
- To identify the specific domains of RasG involved in regulating distinct cellular functions.
Main Methods:
- Expression of activated RasG (RasG-G12T) and its mutants in vegetative Dictyostelium discoideum cells.
- Analysis of cell morphology, including membrane ruffling and F-actin distribution.
- Assessment of cell aggregation following starvation and refeeding.
- Introduction of secondary mutations within the effector domain and flanking regions of RasG-G12T.
Main Results:
- RasG-G12T expression induced significant changes in cell morphology, including altered membrane ruffling and F-actin redistribution.
- RasG-G12T transformants showed impaired rapid contraction upon refeeding and inhibited starvation-induced aggregation.
- Mutations within the RasG effector domain (T35S, Y40C) restored normal morphology and aggregation, indicating effector domain signaling is essential.
- A mutation in the effector distal flanking domain (T45Q) resulted in normal aggregation but retained the altered morphology of RasG-G12T cells.
Conclusions:
- RasG plays a critical role in regulating cytoskeletal organization and cell shape in Dictyostelium discoideum.
- RasG signaling through its effector domain is required for both morphological and developmental changes.
- RasG appears to regulate distinct cellular functions, including cytoskeletal organization and developmental processes, through interaction with multiple downstream effectors.