Immune Netw.  2002 Jun;2(2):102-108. 10.4110/in.2002.2.2.102.

Role of N-terminal Hydrophilic Amino Acids in Molecular Translocation of CTLA-4 to Cell Surface

Affiliations
  • 1Biomedical Research Institute of MedExGen Inc., Seoul, Korea. chungyh@hanyang.ac.kr
  • 2Department of Microbiology, College of Medicine, Hanyang University, Seoul, Korea.
  • 3Division of Life Resources, College of Natural Resources, Taegu University, Gyeongsan, Korea.

Abstract

BACKGROUND: This study was aimed to differentiate two forms of CTLA-4 (CD152) in activated peripheral blood lymphocyte and clarify the mechanism how cytoplasmic form of this molecule is targeted to cell surface.
METHODS
For this purpose we generated 2 different anti-human CD152 peptide antibodies and 5 different N'-terminal deletion mutant CTLA4Ig fusion proteins and carried out a series of Western blot and ELISA analyses. Antipeptide antibodies made in this study were anti-CTLA4pB and anti- CTLA4pN. The former recognized a region on extracellular single V-like domain and the latter recognized N'-terminal sequence of leader domain of human CD152.
RESULTS
In Western blot, the former antibody recognized recombinant human CTLA4Ig fusion protein as an antigen. And this recognition was completely blocked by preincubating antipeptide antibody with the peptide used for the antibody generation at the peptide concentration of 200 ug/ml. These antibodies were recognized human CD152 as a cytoplasmic sequestered- and a membrane bound- forms in phytohemagglutinin (PHA)- stimulated peripheral blood lymphocyte (PBL). These two forms of CD152 were further differentiated by using anti-CTLA4pN and anti-CTLA4pB antibodies such that former recognized cytosolic form only while latter recognized both cytoplasmic- and membrane- forms of this molecule. Furthermore, in a transfection expression study of 5 different N'-terminal deletion mutant CTLA4Ig, mutated proteins were secreted out from transfected cell surface only when more than 6 amino acids from N'-terminal were deleted.
CONCLUSION
Our results implies that cytosolic form of CTLA-4 has leader sequence while membrane form of this molecule does not. And also suggested is that at least N'-terminal 6 amino acid residues of human CTLA-4 are required for regulation of targeting this molecule from cytosolic- to membrane- area of activated human peripheral blood T lymphocyte.

Keyword

CTLA-4; leader sequence; membrane translocation

MeSH Terms

Amino Acids*
Antibodies
Blotting, Western
Cytoplasm
Cytosol
Enzyme-Linked Immunosorbent Assay
Humans
Lymphocytes
Membranes
Staphylococcal Protein A
Transfection
Amino Acids
Antibodies
Staphylococcal Protein A
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