Constitutive internalization of murine MHC class I molecules

J Cell Physiol. 2007 Feb;210(2):445-55. doi: 10.1002/jcp.20877.


The total number of cell surface glycoprotein molecules at the plasma membrane results from a balance between their constitutive internalization and their egress to the cell surface from intracellular pools and/or biosynthetic pathway. Constitutive internalization is net result of constitutive endocytosis and endocytic recycling. In this study we have compared spontaneous internalization of murine major histocompatibility complex (MHC) class I molecules (K(d), D(d), full L(d), and empty L(d)) after depletion of their egress to the cell surface (Cycloheximide [CHX], brefeldin A [BFA]) and internalization after external binding of monoclonal antibody (mAb). MHC class I alleles differ regarding their cell surface stability, kinetics, and in the way of internalization and degradation. K(d) and D(d) molecules are more stable at the cell surface than L(d) molecules and, thus, constitutively internalized more slowly. Although the binding of mAbs to cell surface MHC class I molecules results in faster internalization than depletion of their egress, it is still slow and, thereby, can serve as a model for tracking of MHC class I endocytosis. Internalization of fully conformed MHC class I molecules (K(d), D(d), and L(d)) was neither inhibited by chlorpromazine (CP) (inhibitor of clathrin endocytosis), nor with filipin (inhibitor of lipid raft dependent endocytosis), indicating that fully conformed MHC class I molecules are internalized via the bulk pathway. In contrast, internalization of empty L(d) molecules was inhibited by filipin, indicating that non-conformed MHC class I molecules require intact cholesterol-rich membrane microdomains for their constitutive internalization. Thus, conformed and non-conformed MHC class I molecules use different endocytic pathways for constitutive internalization.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Antibodies, Monoclonal / pharmacology
  • Antifungal Agents / pharmacology
  • BALB 3T3 Cells
  • Cell Line, Tumor
  • Cell Membrane / drug effects
  • Cell Membrane / metabolism*
  • Clathrin / antagonists & inhibitors
  • Clathrin / metabolism
  • Clathrin-Coated Vesicles / drug effects
  • Clathrin-Coated Vesicles / metabolism
  • Endocytosis / drug effects
  • Endocytosis / physiology*
  • Filipin
  • Histocompatibility Antigens Class I / drug effects
  • Histocompatibility Antigens Class I / metabolism*
  • Membrane Microdomains / drug effects
  • Membrane Microdomains / metabolism
  • Mice
  • Protein Binding / drug effects
  • Protein Binding / physiology
  • Protein Synthesis Inhibitors / pharmacology
  • Protein Transport / drug effects
  • Protein Transport / physiology
  • Signal Transduction / drug effects
  • Signal Transduction / physiology
  • Time Factors


  • Antibodies, Monoclonal
  • Antifungal Agents
  • Clathrin
  • Histocompatibility Antigens Class I
  • Protein Synthesis Inhibitors
  • Filipin