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Microtubules and microtubule-associated proteins in resting and mitogenically activated normal human peripheral blood
1Department of Microbiology, Boston University School of Medicine, Massachusetts 02118.
Abstract:
The binding of an appropriate ligand to its specific receptor on the membrane of T cells triggers a cascade of events involved in T cell activation. An important yet unanswered question is how the mitogenic signals are transmitted through the cytoplasm and into the nucleus. The present study was carried out to determine changes in the microtubule (MT) system, following T cell activation. Fluorescence microscopy was employed to examine the organization of the microtubule network in human peripheral blood T cells in response to four different mitogens (phytohemagglutinin, concanavalin A, anti-CD3, and phorbol 12-myristate 13-acetate). The microtubules increase in length, number, and complexity of distribution 20 h after mitogenic stimulation. Using an in situ direct analysis protocol consisting of selective extraction of cells with detergent and Ca2+, 11 protein species, which fulfill the operational definition of microtubule-associated proteins (MAPs), were identified in resting human T cells. Alterations in the expression of these protein species were studied following mitogenic stimulation. These alterations in MAPs expression were also found in purified blast cell fractions indicating that they were specific changes occurring in activated T cell populations. These observations suggest a role for MT and MAPs in the cascade of human T cell activation.
Insights
Human T cell activation involves changes in the microtubule (MT) system. Mitogenic stimulation alters MT organization and microtubule-associated proteins (MAPs) expression, suggesting their role in T cell signaling.
Area of Science:
- Immunology
- Cell Biology
- Cytoskeletal Dynamics
Background:
- T cell activation is initiated by ligand-receptor binding.
- Signal transduction from the cell membrane to the nucleus during T cell activation remains incompletely understood.
- The role of the microtubule (MT) system in T cell activation requires further investigation.
Purpose of the Study:
- To investigate dynamic changes in the microtubule (MT) system during human T cell activation.
- To identify and characterize microtubule-associated proteins (MAPs) in resting and activated T cells.
- To elucidate the potential role of MTs and MAPs in T cell signaling.
Main Methods:
- Human peripheral blood T cells were stimulated with various mitogens (phytohemagglutinin, concanavalin A, anti-CD3, phorbol 12-myristate 13-acetate).
- Fluorescence microscopy was used to analyze microtubule (MT) organization.
- An in situ protocol involving selective cell extraction identified microtubule-associated proteins (MAPs).
Main Results:
- Mitogenic stimulation led to increased length, number, and complexity of microtubule (MT) distribution after 20 hours.
- Eleven microtubule-associated protein (MAP) species were identified in resting T cells.
- Significant alterations in MAP expression were observed in activated T cells, including purified blast cell fractions.
Conclusions:
- Microtubules (MTs) undergo significant organizational changes during T cell activation.
- Microtubule-associated proteins (MAPs) expression is altered following mitogenic stimulation.
- MTs and MAPs likely play a crucial role in the signal transduction cascade of human T cell activation.