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Association of S100B with intermediate filaments and microtubules in glial cells
G Sorci1, A L Agneletti, R Bianchi
1Department of Experimental Medicine and Biochemical Sciences, University of Perugia, Italy.
Insights
The S100B protein interacts with glial intermediate filaments (IFs) and microtubules (MTs), suggesting a role in regulating their dynamics. This protein
Area of Science:
- Cell Biology
- Cytoskeletal Dynamics
- Protein Interactions
Background:
- The Ca2+-regulated S100B protein is known to modulate microtubule (MT) and intermediate filament (IF) assembly-disassembly.
- Understanding S100B's precise localization and interactions within the cell is crucial for elucidating its regulatory functions.
Purpose of the Study:
- To investigate the localization of S100B in relation to GFAP/vimentin IFs and MTs in U251 glial cells.
- To determine how S100B association changes under conditions that alter MT and IF organization.
Main Methods:
- Double immunofluorescence cytochemistry was employed to visualize S100B, GFAP, vimentin, and MTs.
- U251 glial cells were treated with colchicine (MT-depolymerizing agent) and taxol (MT-stabilizing agent).
- Cells were also treated with okadaic acid to induce IF condensation and MT network alterations.
Main Results:
- S100B localized to GFAP/vimentin IFs, MTs, and centrosomes.
- S100B remained associated with IFs upon MT depolymerization and partially followed MTs and IFs upon stabilization.
- Taxol treatment revealed extensive colocalization of S100B with intermingled MTs and IFs, particularly near the nucleus.
Conclusions:
- S100B exhibits dynamic association with both MTs and IFs.
- The findings support S100B's potential role as a key regulator of MT and IF network dynamics in glial cells.
Abstract:
Previous in vitro studies have shown that the Ca2+-regulated S100B protein modulates the assembly-disassembly of microtubules (MTs) and type III intermediate filaments (IFs). In the present report, by double immunofluorescence cytochemistry S 100B was localized to both GFAP/vimentin IFs and MTs as well as to centrosomes in U251 glial cells. In cells treated with the MT-depolymerizing agent, colchicine, S100B remained associated with the rearranged GFAP IFs throughout the cell and, at the cell periphery, vimentin IFs. In cells treated with the MT stabilizing agent, taxol, S100B followed partly the rearrangement of MTs and partly the rearrangement of IFs. Under the latter condition, bundles of MTs with their associated S100B appeared surrounded and/or flanked by rearranged IFs with their associated S100B. Colocalization of S100B with closely arranged IFs and MTs was best evident in cells manipulated with taxol and in triton-cytoskeletons. In these cases, MTs and their associated S100B appeared surrounded and/or flanked by and/or intermingled with IFs and their associated S100B. Also, a preferential association of S100B with GFAP vs. vimentin IFs could be observed near the nucleus where colocalization of S100B with MTs was also maximal. Condensation of IFs and alteration of the MT network caused by treatment of cells with the phosphatase inhibitor, okadaic acid, resulted in a concomitant condensation/alteration of the S100B immunoreactivity. The present results lend support to the possibility that S100B may be an important factor implicated in the regulation of the dynamics of MTs and IFs.