Is receptor cleavage into two subunits necessary for thyrotropin action?
Unlike the wild-type thyrotropin (TSH) receptor, the chimeric TSH-LH/CG receptor TSH-LHR-14 does not cleave into two subunits when cross-linked to [125I]TSH on the surface of intact cells. Immunoblotting of TSH-LHR-14 in whole cell homogenates demonstrated that only a single chain receptor was detected under reducing conditions. TSH-LHR-14, like the A subunit of another chimeric receptor (TSH-LHR-10) that does cleave into two subunits, was almost entirely resistant to endoglycosidase H, indicating that it contains predominantly complex carbohydrate. The fact that TSH-LHR-14 reaches the cell surface where it binds TSH with high affinity and transduces a signal indicates that receptor cleavage into two subunits is not a prerequisite for TSH action.
Chazenbalk
G D
GD
Thyroid Molecular Biology Unit, Veterans' Administration Medical Center, San Francisco, California 94121, USA.
McLachlan
S M
SM
Nagayama
Y
Y
Rapoport
B
B
D000818:Animals; D015153:Blotting, Western; D016466:CHO Cells; D002241:Carbohydrates / Q000032:analysis; D006224:Cricetinae; D006031:Glycosylation; D006868:Hydrolysis; D011974:Receptors, LH / Q000235:genetics / Q000378:metabolism; D011989:Receptors, Thyrotropin / Q000235:genetics / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D013972:Thyrotropin / Q000378:metabolism*
D002241:Carbohydrates; D011974:Receptors, LH; D011989:Receptors, Thyrotropin; D011993:Recombinant Fusion Proteins; D013972:Thyrotropin