HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

J. Biol. Chem., Vol. 280, Issue 25, 23660-23667, June 24, 2005

This Article Full Text Full Text (PDF) All Versions of this Article: 280/25/23660    most recent M500128200v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Ching, K. H. Articles by Burbelo, P. D. Search for Related Content PubMed PubMed Citation Articles by Ching, K. H. Articles by Burbelo, P. D. Social Bookmarking                      What's this?

The Role of SPECs, Small Cdc42-binding Proteins, in F-actin Accumulation at the Immunological Synapse^*

Kathryn H. Ching, Adam E. Kisailus, and Peter D. Burbelo

From the Lombardi Comprehensive Cancer Center, Department of Oncology, and the Department of Biochemistry and Molecular Biology, Georgetown University Medical Center, Washington, D. C. 20057

SPEC1 and SPEC2 are structurally similar Cdc42-binding proteins of 79 and 84 amino acid residues, respectively. We investigated the role of SPEC2 in T cell function due to its high mRNA expression in lymphocytes. Western blot analysis revealed abundant SPEC2 protein in lymphocytes, which in glutathione S-transferase-capture experiments specifically interacted with only GTP-bound Cdc42. Immunofluorescence experiments revealed that the SPEC2 protein was diffusely localized in the cytoplasm and at the cell membrane in unstimulated Jurkat T cells and Raji B cells. Recruitment of SPEC2 within Jurkat T cells to the antigen-presenting cell interface occurred following incubation with staphylococcal enterotoxin E superantigen-loaded B cells and colocalized there with F-actin and Cdc42. T cell receptor (TCR) activation studies using anti-CD3 antibody-coated polystyrene beads showed that SPEC2 was recruited to the site of bead contact, which was not observed with anti-major histocompatibility complex antibody-coated beads. Accumulation of SPEC2 following TCR engagement occurred as early as 5 min, before obvious F-actin accumulation. Biochemical studies with Jurkat T cells demonstrated that N-terminal cysteine residues in SPEC2 were palmitoylated. Overexpression studies of the related SPEC1 showed that it also was recruited to the activated TCR. Mutational analysis revealed that localization of SPEC1 to the TCR required two N-terminal cysteine residues. Furthermore, a SPEC1 Cdc42 Rac-interacting binding mutant, containing an intact N terminus but defective in Cdc42 binding, completely blocked F-actin accumulation at the activated TCR. Taken together these results suggest that SPECs may play important roles in Cdc42-mediated F-actin accumulation at the immunological synapse.

Received for publication, January 5, 2005 , and in revised form, April 4, 2005.

^* This work was supported by funding through the Susan G. Komen Foundation (Grant 9851) (to P. D. B.) and a DOD breast cancer predoctoral fellowship (to K. H. C.). The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

To whom correspondence should be addressed: Rm. W218 New Research Bldg., Lombardi Comprehensive Cancer Center, 3970 Reservoir Rd, NW, Georgetown University Medical Center, Washington, D. C. 20057. Tel.: 202-687-1444; Fax: 202-687-7505; E-mail: burbelpd{at}georgetown.edu.

CiteULike    Complore    Connotea    Del.icio.us    Digg    Reddit    Technorati    What's this?

This article has been cited by other articles:

				F. Allantaz, D. Chaussabel, D. Stichweh, L. Bennett, W. Allman, A. Mejias, M. Ardura, W. Chung, C. Wise, K. Palucka, et al. Blood leukocyte microarrays to diagnose systemic onset juvenile idiopathic arthritis and follow the response to IL-1 blockade J. Exp. Med., September 3, 2007; 204(9): 2131 - 2144. [Abstract] [Full Text] [PDF]