Inefficient assembly limits transport and cell surface expression of HLA-Cw4 molecules in C1R

Tissue Antigens. 1996 Dec;48(6):651-61. doi: 10.1111/j.1399-0039.1996.tb02688.x.

Abstract

HLA-C antigens are expressed to the cell surface at roughly 10% the level of HLA-B or -A, and their serological definition remains persistently difficult. To characterize the factors limiting surface expression, the processes of assembly and intracellular transport of HLA-Cw4 molecules were investigated in the C1R cell line. When appropriate peptides were added to cultured cells or in cell lysates significant amounts of conformed HLA-C molecules that associate with beta 2-microglobulin (beta 2 m) are detected, but are indeed not sufficient to restore expression to the level observed for HLA-A or -B molecules. Furthermore, a precursor/product relationship exists between the free class I heavy chain and the mature conformation of HLA-Cw4 molecules. Thus, HLA-C assembly promotes the conversion of HC-10-reactive molecules (weakly-beta 2m-associated non-ligand associated free HC form) into the beta 2m-associated class I molecules recognized by W6/32. To further investigate the factors that regulate cell surface expression, intracellular transport of HLA-Cw4 was studied in pulse chase analysis. In contrast to some HLA-A and B, maturation of HLA-Cw4 heavy chains and their export to the medial and trans-Golgi compartments are quite inefficient. After 4 h of chase period, roughly half of the pulse-labeled HLA-Cw4 molecules have transited to the medial-Golgi and acquired complex oligosaccharides characteristic of mature form. In addition, treatment with gamma-interferon does not appear to improve maturation of HLA-Cw4 heavy chains, suggesting that increased supply of peptides does not influence intracellular transport. Moreover, only a small fraction in the pool of HLA-Cw4 molecules was subsequently transported through the trans-Golgi network, as indicated by their acquisition of sialic acids. Taken together these studies show that HLA-Cw4 molecules are inefficiently transported through the Golgi apparatus and presumably retained in the endoplasmic reticulum or cis-Golgi compartment.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Biological Transport
  • Cell Line, Transformed
  • Cell Membrane
  • Gene Products, env / chemical synthesis
  • Gene Products, env / pharmacology
  • Golgi Apparatus / metabolism
  • HLA-C Antigens / chemistry*
  • HLA-C Antigens / immunology*
  • Humans
  • Interferon-gamma / pharmacology
  • Ligands
  • Oligosaccharides / chemistry
  • Oligosaccharides / immunology
  • Peptides / pharmacology
  • Protein Conformation

Substances

  • Gene Products, env
  • HLA-C Antigens
  • HLA-C*04 antigen
  • Ligands
  • Oligosaccharides
  • Peptides
  • Interferon-gamma