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The cytoplasmic tail of L-selectin interacts with members of the ezrin-radixin-moesin (ERM) family of proteins: activation-dependent binding of moesin but not ezrin

Ivetic, Aleksander, Deka, Jurgen, Ridley, Anne and Ager, Ann 2001. The cytoplasmic tail of L-selectin interacts with members of the ezrin-radixin-moesin (ERM) family of proteins: activation-dependent binding of moesin but not ezrin. Journal of Biological Chemistry 277 (3) , pp. 2321-2329. 10.1074/jbc.M109460200

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Abstract

L-selectin regulates the recruitment of naïve lymphocytes from the bloodstream to secondary lymphoid organs, mediating their initial capture and subsequent rolling along high endothelial cell surface-expressed ligands in peripheral lymph nodes. In vivo, distribution of L-selectin and cell surface levels determine the tethering efficiency and rolling velocity of leukocytes, respectively. Treatment of naïve lymphocytes with phorbol myristate acetate (PMA) induces rapid ectodomain proteolytic down-regulation (shedding) of surface L-selectin via a protein kinase C (PKC)-dependent pathway. In an attempt to isolate proteins that are involved in regulating L-selectin expression, an affinity column was constructed using the 17 amino acid cytoplasmic tail of L-selectin. Affinity purification of extracts from lymphocytes, pre-treated with or without PMA, allowed identification of proteins that interact with the affinity column under one condition but not the other. Using this approach members of the Ezrin-Radixin-Moesin (ERM) family of proteins were found to interact specifically with the cytoplasmic tail of L-selectin. Moesin from PMA-stimulated lymphocytes, but not from unstimulated lymphocytes, bound to L-selectin tail. In contrast, ezrin from unstimulated or PMA-stimulated lymphocytes associated with L-selectin tail with equal affinity. Furthermore, the protein kinase C (PKC) inhibitor Ro 31-8220 significantly reduced the interaction of moesin, but not ezrin, with L-selectin. Alanine mutations of membrane-proximal basic amino acid residues in the cytoplasmic domain of L-selectin identified arginine 357 as a critical residue for both ezrin and moesin interaction. Finally, BIAcore affinity analysis confirmed that N-terminal moesin interacts specifically with L-selectin cytoplasmic tail, with relatively high affinity (Kd ª 40 nM). Based on these findings, although moesin and ezrin bind to a similar region of the cytoplasmic tail of L-selectin, moesin binding is dependent on PKC activation which suggests that ezrin and moesin are regulated differently in lymphocytes.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Medicine
Systems Immunity Research Institute (SIURI)
Subjects: R Medicine > R Medicine (General)
Publisher: American Society for Biochemistry and Molecular Biology
ISSN: 0021-9258
Last Modified: 04 Jun 2017 04:08
URI: http://orca-mwe.cf.ac.uk/id/eprint/33332

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