Identification of a proline-rich sequence in the CD2 cytoplasmic domain critical for regulation of integrin-mediated adhesion and activation of phosphoinositide 3-kinase

Wendy J. Kivens, Stephen W. Hunt, James L. Mobley, Traci Zell, Cheryl L. Dell, Barbara E. Bierer, Yoji Shimizu

Research output: Contribution to journalArticlepeer-review

41 Scopus citations

Abstract

The CD2 molecule is one of several lymphocyte receptors that rapidly initiates signaling events regulating integrin-mediated cell adhesion. CD2 stimulation of resting human T cells results within minutes in an increase in β1-integrin-mediated adhesion to fibronectin. We have utilized the HL60 cell line to map critical residues within the CD2 cytoplasmic domain involved in CD2 regulation of integrin function. A panel of CD2 cytoplasmic domain mutants was constructed and analyzed for their ability to upregulate integrin-mediated adhesion to fibronectin. Mutations in the CD2 cytoplasmic domain implicated in CD2-mediated interleukin-2 production or CD2 avidity do not affect CD2 regulation of integrin activity. A proline-rich sequence, K- G-P-P-L-P (amino acids 299 to 305), is essential for CD2-mediated regulation of β1 integrin activity. CD2-induced increases in β1 integrin activity could be blocked by two phosphoinositide 3-kinase (PI 3-K) inhibitors or by overexpression of a dominant negative form of the p85 subunit of PI 3-K. In addition, CD2 cytoplasmic domain mutations that abrogate CD2-induced increases in integrin-mediated adhesion also ablate CD2-induced increases in PI 3-K enzymatic activity. Surprisingly, CD2 cytoplasmic domain mutations that inhibit CD2 regulation of adhesion do not affect the constitutive association of the p85 subunit of PI 3-K association with CD2. Mutation of the proline residues in the K-G-P-P-L-P motif to alanines prevented CD2- mediated activation of integrin function and PI 3-K activity but not mitogen- activated protein (MAP) kinase activity. Furthermore, the MEK inhibitor PD 098059 blocked CD2-mediated activation of MAP kinase but had no effect on CD2-induced adhesion. These studies identify a proline-rich sequence in CD2 critical for PI 3-K-dependent regulation of β1 integrin adhesion by CD2. In addition, these studies suggest that CD2-mediated activation of MAP kinase is not involved in CD2 regulation of integrin adhesion.

Original languageEnglish (US)
Pages (from-to)5291-5307
Number of pages17
JournalMolecular and cellular biology
Volume18
Issue number9
DOIs
StatePublished - 1998

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