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Regulation of integrin gene expression by substrate adherence.
1Department of Cellular and Structural Biology, University of Texas Health Science Center, San Antonio 78284.
The Journal of Biological Chemistry
|November 25, 1992
Summary
Cell suspension upregulates specific integrin alpha-subunits, like alpha-2 and alpha-4, in MG-63 osteosarcoma cells. This demonstrates a novel mechanism for differential integrin gene expression control.
Area of Science:
- Cell Biology
- Molecular Biology
- Biochemistry
Background:
- Integrin gene expression is typically regulated by factors like TGF-β, IL-1β, and prostaglandins under adherent conditions.
- Cellular microenvironment, including substrate adherence, significantly influences gene expression patterns.
- Previous research has noted changes in gene expression due to altered cell shape.
Purpose of the Study:
- To investigate a novel mechanism regulating integrin gene expression.
- To determine if non-adherent conditions differentially control integrin expression.
- To explore the role of cell suspension in modulating integrin subunit mRNA and protein levels.
Main Methods:
- Culturing MG-63 osteosarcoma cells under both substrate adherent and suspension conditions.
- Quantifying mRNA levels of various integrin alpha-subunits (e.g., alpha-2, alpha-4, alpha-v, alpha-5) using techniques like quantitative PCR.
- Confirming changes at the protein level using immunocytochemistry.
- Treating cells with cytochalasin B and phorbol ester to assess their effect on integrin subunit expression.
Main Results:
- Maintaining MG-63 cells in suspension led to a significant upregulation of integrin alpha-2 (4-fold) and alpha-4 (6-fold) mRNA levels within 4 hours.
- mRNA levels for alpha-2, alpha-4, and alpha-v subunits were markedly increased in several differentiated cell lines under non-adherent conditions.
- The alpha-5 subunit did not show upregulation during suspension growth.
- Cytochalasin B and a phorbol ester induced alpha-2 subunit expression in a dose-dependent manner, but not alpha-4 or alpha-5.
- Changes in mRNA levels were corroborated by protein level changes observed via immunocytochemistry.
Conclusions:
- Lack of substrate adherence represents a novel mechanism for the differential control of integrin gene expression.
- Cell suspension can induce the upregulation of specific integrin alpha-subunits, impacting cellular behavior.
- These findings contribute to understanding how cellular microenvironment and shape influence integrin expression, potentially through altered gene regulation pathways.