THE BASOLATERAL LOCALIZATION SIGNAL OF THE FOLLICLE-STIMULATING-HORMONE RECEPTOR

The follicle-stimulating hormone receptor (FSHR) is physiologically lo calized in the basolateral compartment of the membrane of Sertoli cell s. This localization is also observed when the receptor is experimenta lly expressed in Madin-Darby canine kidney cells. We thus used in vitr o mutagenesis and transfection into these polarized cells to delineate the basolateral localization signal of the receptor. The signal was l ocalized in the C-terminal tail of the intracellular domain (amino aci ds 678-691) at a marked distance of the membrane. Mutation of individu al amino acids highlighted the importance of Tyr(684) and Leu(689). Th e 14-amino acid sequence was grafted onto the p75 neurotrophin recepto r and redirected this apical protein to the basolateral cell membrane compartment, Deletion of amino acids 677-695 did not modify the intern alization of the FSHR, showing that the basolateral localization signa l of the FSHR is not colinear with its internalization signal.