The extracellular domain of the TGFbeta type II receptor regulates membrane raft partitioning

• Published in: Biochemical journal Vol. 421; no. 1; p. 119
• Main Authors: Luga, Valbona, McLean, Sarah, Le Roy, Christine, O'Connor-McCourt, Maureen, Wrana, Jeffrey L, Di Guglielmo, Gianni M
• Format: Journal Article
• Language: English
• Published: England 12.06.2009
• Subjects: Animals; Caveolin 1 - metabolism; Cell Line; Cell Membrane - chemistry; Cell Membrane - metabolism; Glycosylation; Granulocyte-Macrophage Colony-Stimulating Factor; Humans; Membrane Microdomains - metabolism; Mink; Mutation; Protein-Serine-Threonine Kinases - chemistry; Protein-Serine-Threonine Kinases - metabolism; Receptors, Transforming Growth Factor beta - chemistry; Receptors, Transforming Growth Factor beta - metabolism; Recombinant Proteins; Tunicamycin - pharmacology
• ISSN: 1470-8728
• DOI: 10.1042/BJ20081131

Cell-surface TGFbeta (transforming growth factor beta) receptors partition into membrane rafts and the caveolin-positive endocytic compartment by an unknown mechanism. In the present study, we investigated the determinant in the TGFbeta type II receptor (TbetaRII) that is necessary for membrane raft/caveolar targeting. Using subcellular fractionation and immunofluorescence microscopy techniques, we demonstrated that the extracellular domain of TbetaRII mediates receptor partitioning into raft and caveolin-positive membrane domains. Pharmacological perturbation of glycosylation using tunicamycin or the mutation of Mgat5 [mannosyl(alpha-1,6)-glycoprotein beta-1,6-N-acetylglucosaminyltransferase V] activity interfered with the raft partitioning of TbetaRII. However, this was not due to the glycosylation state of TbetaRII, as a non-glycosylated TbetaRII mutant remained enriched in membrane rafts. This suggested that other cell-surface glycoproteins associate with the extracellular domain of TbetaRII and direct their partitioning in membrane raft domains. To test this we analysed a GMCSF (granulocyte/macrophage colony-stimulating factor)-TbetaRII chimaeric receptor, which contains a glycosylated GMCSF extracellular domain fused to the transmembrane and intracellular domains of TbetaRII. This chimaeric receptor was found to be largely excluded from membrane rafts and caveolin-positive structures. Our results indicate that the extracellular domain of TbetaRII mediates receptor partitioning into membrane rafts and efficient entrance into caveolin-positive endosomes.