A novel ligand in lymphocyte-mediated cytotoxicity: expression of the beta subunit of H+ transporting ATP synthase on the surface of tumor cell lines

J Exp Med. 1994 Jul 1;180(1):273-81. doi: 10.1084/jem.180.1.273.

Abstract

Extracellular adenosine triphosphate (eATP) has been suggested to play a role in lymphocyte-induced tumor destruction. We now provide evidence that a protein responsible for ATP synthesis in mitochondria may also play a physiologic role in major histocompatibility complex-independent, lymphocyte-mediated cytotoxicity. A 51.5-kD protein (p51.5) bearing structural and immunologic characteristics of the beta subunit of H+ transporting ATP synthase (E.C. 3.6.1.34, beta-H+ATPase, published molecular mass of 51.6 kD) was detected on the plasma membrane of three different human tumor cell lines studied. NH2-terminal amino acid sequence analysis of purified p51.5 from K562 tumor cells revealed 100% homology of 16 residues identified in the first 21 positions to the known sequence of human mitochondrial beta-H+ ATPase. Antibody directed against a 21-mer peptide in the ATP binding region of beta-H+ ATPase (anti-beta) reacted with only one band on Western blots of whole tumor extracts and tumor membrane extracts suggesting that the antiserum reacts with a single species of protein. Anti-beta reacted with the cell membranes of tumor cells as determined by fluorescence-activated flow cytometry and immunoprecipitated a 51.5-kD protein from surface-labeled neoplastic cells (but not human erythrocytes and lymphocytes). Purified p51.5 bound to human lymphocytes and inhibited natural killer (NK) cell-mediated cytotoxicity. Furthermore, anti-beta treatment of the K562 and A549 tumor cell lines inhibited NK (by > 95%) and interleukin 2-activated killer (LAK) cell (by 75%) cytotoxicity, respectively. Soluble p51.5 upon binding to lymphocytes retained its reactivity to anti-beta suggesting that the ATP binding domain and the lymphocyte-receptor binding domain reside in distinct regions of the ligand. These results suggest that beta-H+ ATPase or a nearly identical molecule is an important ligand in the effector phase (rather than the recognition phase) of a cytolytic pathway used by naive NK and LAK cells.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Amino Acid Sequence
  • Cytotoxicity, Immunologic*
  • Humans
  • Leukemia, Erythroblastic, Acute / metabolism
  • Ligands
  • Membrane Proteins / chemistry
  • Membrane Proteins / immunology
  • Membrane Proteins / metabolism*
  • Molecular Sequence Data
  • Neoplasm Proteins / chemistry
  • Neoplasm Proteins / immunology
  • Neoplasm Proteins / metabolism*
  • Proton-Translocating ATPases / metabolism*
  • T-Lymphocytes / immunology*
  • T-Lymphocytes / metabolism
  • Tumor Cells, Cultured

Substances

  • Ligands
  • Membrane Proteins
  • Neoplasm Proteins
  • Proton-Translocating ATPases