Microtubules and microtubule-associated proteins in resting and mitogenically activated normal human peripheral blood T cells.

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.