title: Differential recognition of a tyrosine-dependent signal in the basolateral and endocytic pathways of thyroid epithelial cells.
abstract: Trafficking of receptors is of crucial importance for the physiology of most exocrine and endocrine organs. It is not known yet if the same mechanisms are used for sorting in the exocytic and endocytic pathways in the different epithelial tissues. In this work, we have used a deletion mutant of the human neurotrophin receptor p75(hNTR) that is normally localized on the apical membrane when expressed in Madin-Darby canine kidney cells. This internal 57-amino acid deletion of the cytoplasmic tail leads to a relocation of the protein from the apical to the basolateral membrane and to rapid and efficient endocytosis. These events are mediated by a signal localized within 9 amino acids of the mutated cytoplasmic tail that is strictly dependent on a tyrosine residue (Tyr-308). We have analyzed the basolateral sorting efficiency and endocytic capacity of this signal in Fischer rat thyroid (FRT) cells, in which basolateral and endocytic determinants have not yet been identified. We found that this targeting signal can mediate efficient transport to the basolateral membrane also in FRT cells with similar tyrosine dependence as in MDCK cells. In contrast to MDCK cells, this Tyr-based signal was not able to mediate coated pits localization and endocytosis in FRT cells. These data represent the first characterization of basolateral/endocytic signals in thyroid epithelial cells. Furthermore, our results indicate that requirements for tyrosine-dependent basolateral sorting signals are conserved among cell lines from different tissues but that the recognition of the colinear endocytic signal is tissue specific.
authors.affiliation: Centro di Endocrinologia ed Oncologia Sperimentale del Centro Nazionale delle Ricerche-Dipartimento di Biologia e Patologia Cellulare e Molecolare, Università degli Studi di Napoli Federico II, 80131 Napoli, Italy.
authors.forename: Concetta
authors.initials: C
authors.lastname: Lipardi
authors.forename: Germana
authors.initials: G
authors.lastname: Ruggiano
authors.forename: Lorena
authors.initials: L
authors.lastname: Perrone
authors.forename: Simona
authors.initials: S
authors.lastname: Paladino
authors.forename: Laure
authors.initials: L
authors.lastname: Monlauzeur
authors.forename: Lucio
authors.initials: L
authors.lastname: Nitsch
authors.forename: André
authors.initials: A
authors.lastname: Le Bivic
authors.forename: Chiara
authors.initials: C
authors.lastname: Zurzolo
mesh_terms: D000818:Animals; D001710:Biotin / Q000378:metabolism; D002478:Cells, Cultured; D002999:Clone Cells; D004285:Dogs; D004705:Endocytosis / Q000235:genetics / Q000502:physiology*; D004847:Epithelial Cells / Q000502:physiology*; D019084:Fluorescent Antibody Technique, Indirect; D006801:Humans; D008566:Membranes / Q000378:metabolism; D008854:Microscopy, Electron; D009154:Mutation / Q000235:genetics; D020932:Nerve Growth Factor / Q000378:metabolism; D051381:Rats; D011916:Rats, Inbred F344; D020800:Receptor, Nerve Growth Factor; D011956:Receptors, Cell Surface / Q000378:metabolism; D017475:Receptors, Nerve Growth Factor / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction / Q000235:genetics / Q000502:physiology*; D013961:Thyroid Gland / Q000166:cytology / Q000502:physiology*; D014162:Transfection; D014443:Tyrosine / Q000502:physiology*
chemical_list: D020800:Receptor, Nerve Growth Factor; D011956:Receptors, Cell Surface; D017475:Receptors, Nerve Growth Factor; D014443:Tyrosine; D001710:Biotin; D020932:Nerve Growth Factor