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Published on: July 30, 2014
Cytosolic SYT/SS18 isoforms are actin-associated proteins that function in matrix-specific adhesion
Jaehong Kim1, Mei Swee, William C Parks
1Center for Lung Biology, University of Washington, Seattle, Washington, United States of America.
Plos One
|August 4, 2009
Summary
Synovial sarcoma translocated gene (SYT) proteins, known nuclear coactivators, also function in the cytosol. Cytoplasmic SYT interacts with actin filaments, impacting cell adhesion and spreading on specific extracellular matrices.
Area of Science:
- Cell Biology
- Molecular Biology
- Biochemistry
Background:
- The Synovial sarcoma Translocated gene (SYT), also known as SS18, is primarily recognized for its nuclear role as a transcriptional coactivator.
- SYT exists in two main isoforms, SYT/L and SYT/S, with established functions within the nucleus.
Purpose of the Study:
- To investigate the subcellular localization and function of SYT isoforms beyond the nucleus.
- To determine the relationship between SYT isoforms and the actin cytoskeleton.
- To elucidate the role of cytoplasmic SYT in cell adhesion and response to extracellular matrices.
Main Methods:
- Utilized isoform-specific antibodies to detect SYT localization in the cytosol.
- Performed co-immunoprecipitation and co-sedimentation assays to assess interactions with actin and actin-associated proteins.
- Employed RNA interference (RNAi) to ablate SYT isoforms and observed effects on cellular structures and adhesion.
- Tested cell adhesion and spreading on various extracellular matrix proteins.
Main Results:
- A significant pool of SYT isoforms was found organized in filamentous arrays within the cytosol.
- SYT isoforms co-immunoprecipitated and co-localized with the actin cytoskeleton, associating with actin bundles but not focal adhesions.
- Disruption of the actin cytoskeleton led to the breakdown of SYT filamentous organization.
- RNAi-mediated ablation of SYT impaired stress fiber and focal adhesion formation, and significantly reduced cell adhesion and spreading on fibronectin and laminin-111.
Conclusions:
- Cytoplasmic SYT isoforms interact with actin filaments, suggesting a novel extranuclear function.
- SYT plays a crucial role in regulating cell adhesion and spreading, particularly in response to specific extracellular matrix components like fibronectin and laminin-111.
- These findings reveal a dual role for SYT in both nuclear transcriptional regulation and cytoplasmic cytoskeletal dynamics and cell adhesion.
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