CD-3-mediated activation of MAP-2 kinase can be modified by ligation of the CD4 receptor. Evidence for tyrosine phosphorylation during activation of this kinase

UMMS Affiliation

Department of Molecular Genetics and Microbiology

Publication Date


Document Type



Adult; Antigens, CD3; Antigens, CD4; Antigens, Differentiation, T-Lymphocyte; Calcium; Calcium-Calmodulin-Dependent Protein Kinases; Enzyme Activation; Humans; Phosphorylation; Protein Kinases; Receptors, Antigen, T-Cell; Tetradecanoylphorbol Acetate; Tyrosine


Microbiology | Molecular Genetics


The CD4R has been shown to exert variable effects on T cell activation responses. Depending on the manner of ligation, the CD4R has been demonstrated to have positive as well as negative effects on the generation of [Ca2+]i flux by the CD3R. Coaggregation of CD3 with CD4 enhanced Ca2+ flux while their independent ligation and aggregation diminished this response. To further elucidate these paradoxical CD4 effects, we studied induction of a microtubule-associated protein 2 kinase (MAP-2K) activity during ligation of the CD3R. Lymphoid MAP-2K activation by CD3 is an evanescent event that is dependent on phosphorylation of 43-kDa MAP-2K via a pathway that involves protein kinase C. Coaggregation of CD4 and CD3 with cross-linking antibodies and avidin enhanced the CD3-mediated MAP-2K response almost twofold. In contrast, independent ligation and cross-linking of CD4 reduced the CD3-induced MAP-2K response by approximately 50%. An important requirement for this inhibitory effect was that CD4 be ligated before stimulation with anti-CD3. The negative effect of anti-CD4 mAb was specific as other mAb failed to simulate this event. The PMA-induced MAP-2K response was not inhibited by anti-CD4. Intact 32P-labeled Jurkat and normal human T cells demonstrated the appearance of a single 43-kDa tyrosine phosphoprotein during stimulation with PMA and anti-CD3. When these crude cellular extracts were extensively fractionated across DEAE- and hydrophobic columns, MAP-2K was resolved into two peaks of activity, each containing a single tyrosine phosphoprotein around 43 kDa. In addition to tyrosine-specific labeling, mitogenic stimulation of normal human T cells also induced threonine-specific labeling of MAP-2K. These results imply that activation of lymphoid MAP-2K is a dual process requiring at least two independent kinases for optimal activity. Inasmuch as CD3 activates protein kinase C and CD4 is associated with a tyrosine kinase, pp56lck, we suggest that their coaggregation may create the conditions whereby MAP-2K may be activated by dual phosphorylation. Independent aggregation of these receptors may lead to physical separation and breakdown of this interactive mechanism.


J Immunol. 1990 Aug 1;145(3):971-9.

Journal/Book/Conference Title

Journal of immunology (Baltimore, Md. : 1950)

Related Resources

Link to Article in PubMed