title: Cathepsin X cleavage of the beta2 integrin regulates talin-binding and LFA-1 affinity in T cells.
abstract: T cell migration, essential for immune surveillance and response, is mediated by the integrin LFA-1. CatX, a cysteine carboxypeptidase, is involved in the regulation of T cell migration by interaction with LFA-1. We show that sequential cleavage of C-terminal amino acids from the β(2) cytoplasmic tail of LFA-1, by CatX, enhances binding of the adaptor protein talin to LFA-1 and triggers formation of the latter's high-affinity form. As shown by SPR analysis of peptides constituting the truncated β(2) tail, the cleavage of three C-terminal amino acids by CatX resulted in a 1.6-fold increase of talin binding. Removal of one more amino acid resulted in a 2.5-fold increase over the intact tail. CatX cleavage increased talin-binding affinity to the MD but not the MP talin-binding site on the β(2) tail. This was shown by molecular modeling of the β(2) tail/talin F3 complex to be a result of conformational changes affecting primarily the distal-binding site. Analysis of LFA-1 by conformation-specific mAb showed that CatX modulates LFA-1 affinity, promoting formation of high-affinity from intermediate-affinity LFA-1 but not the initial activation of LFA-1 from a bent to extended form. CatX post-translational modifications may thus represent a mechanism of LFA-1 fine-tuning that enables the trafficking of T cells.
authors: University of Ljubljana, Askerceva 7, 1000 Ljubljana, Slovenia. zala.jevnikar@ffa.uni-lj.si
authors: Zala
authors: Z
authors: Jevnikar
authors: Natasa
authors: N
authors: Obermajer
authors: Bojan
authors: B
authors: Doljak
authors: Samo
authors: S
authors: Turk
authors: Stanislav
authors: S
authors: Gobec
authors: Urban
authors: U
authors: Svajger
authors: Stephan
authors: S
authors: Hailfinger
authors: Margot
authors: M
authors: Thome
authors: Janko
authors: J
authors: Kos
mesh_terms: D015153:Blotting, Western; D018821:CD18 Antigens / Q000737:chemistry / Q000378:metabolism*; D002403:Cathepsins / Q000737:chemistry / Q000378:metabolism*; D002469:Cell Separation; D002634:Chemotaxis, Leukocyte / Q000502:physiology*; D004591:Electrophoresis, Polyacrylamide Gel; D005434:Flow Cytometry; D006801:Humans; D047468:Immunoprecipitation; D019169:Jurkat Cells; D016169:Lymphocyte Function-Associated Antigen-1 / Q000737:chemistry / Q000378:metabolism*; D008856:Microscopy, Fluorescence; D008958:Models, Molecular; D016133:Polymerase Chain Reaction; D011485:Protein Binding; D011499:Protein Processing, Post-Translational / Q000276:immunology; D013601:T-Lymphocytes / Q000276:immunology / Q000378:metabolism*; D016608:Talin / Q000737:chemistry / Q000378:metabolism*; D014162:Transfection
chemical_list: D018821:CD18 Antigens; D016169:Lymphocyte Function-Associated Antigen-1; D016608:Talin; D002403:Cathepsins