Cysteine-699, a possible palmitoylation site of the thyrotropin receptor, is not crucial for cAMP or phosphoinositide signaling but is necessary for full surface expression.
We investigated the role of the cysteine residues in the cytoplasmic tail of the thyrotropin receptor (TSHR) in TSH binding and signal transduction by individually mutating two cysteine residues to serine. Neither mutant exhibited changes in basal, TSH- or Graves' IgG-stimulated cAMP or inositol phosphate responses. However, mutation of Cys-699 significantly decreased TSH binding Bmax without significantly changing binding affinity, amount or sizes of TSHR forms on Western blots. These findings suggest that Cys-699, which is a potential site for lipid modification and whose equivalent in other receptors was shown to be palmitoylated, is important for efficiency of proper membrane insertion and/or stability of the receptor.
Kosugi
S
S
Department of Laboratory Medicine, Kyoto University School of Medicine, Japan.
Mori
T
T
D000595:Amino Acid Sequence; D000818:Animals; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D000242:Cyclic AMP / Q000378:metabolism*; D003545:Cysteine / Q000378:metabolism*; D008969:Molecular Sequence Data; D019308:Palmitic Acid; D010169:Palmitic Acids / Q000378:metabolism*; D010716:Phosphatidylinositols / Q000378:metabolism*; D011485:Protein Binding; D011989:Receptors, Thyrotropin / Q000737:chemistry / Q000378:metabolism*; D015398:Signal Transduction; D013972:Thyrotropin / Q000378:metabolism
D010169:Palmitic Acids; D010716:Phosphatidylinositols; D011989:Receptors, Thyrotropin; D019308:Palmitic Acid; D013972:Thyrotropin; D000242:Cyclic AMP; D003545:Cysteine