PMID: 19556306

 

    Legend: Sugar

Title : Mutational analysis of Cys(88) of Toll-like receptor 4 highlights the critical role of MD-2 in cell surface receptor expression

Abstract :
  1. The role of MD-2 in cell surface expression of Toll-like receptor ( TLR ) 4 has been controversial
  2. The purposes of this study were to characterize the N-glycan of TLR4 and to investigate the roles of MD-2 in N-linked glycosylation and cell surface expression of TLR4
  3. Lectin blot and cell surface biotinylation revealed that TLR4 exhibited the 110 kDa protein with high mannose type N-glycans and the 130 kDa protein with complex type N-glycans and that only the 130 kDa TLR4 with complex type N-glycans was expressed on the cell surface
  4. The cells transfected with a mutant TLR4 ( C88A ) alone expressed only the 110 kDa TLR4 with a high mannose type N-glycan, which did not appear on the cell surface
  5. However, TLR4 ( C88A ) acquired complex type N-glycans and was expressed on the cell surface when MD-2 was co-transfected
  6. The amount of the 130 kDa TLR4 ( C88A ) with complex type N-glycans expressed on the cell surface depended on that of MD-2 transfected
  7. alpha-Mannosidase II inhibitor blocked the processing N-glycans to complex type , but TLR4 with high mannose type appeared on the cell surface, suggesting that TLR4 is destined to locate on the cell surface before processing N-glycans from a high mannose type to a complex type
  8. From these results, we conclude that MD-2 is critical for cell surface expression of TLR4 ( C88A )
  9. This study provides evidence that MD-2 possesses potential ability to play an essential role in cell surface expression of TLR4