Expression and Distribution of MAL2, an Essential Element of the Machinery for Basolateral-to-Apical Transcytosis, in Human Thyroid Epithelial Cells

  1. Marazuela, Mónica 2
  2. Martín-Belmonte, Fernando 1
  3. García-López, María Angeles 2
  4. Aranda, Juan F. 1
  5. de Marco, María C. 1
  6. Alonso, Miguel A. 1
  1. 1 Centro de Biología Molecular “Severo Ochoa”, Universidad Autonoma de Madrid and Consejo Superior de Investigaciones Cientificas, 28049 Madrid, Spain
  2. 2 Departamento de Endocrinología, Hospital de la Princesa, 28006 Madrid, Spain
Revista:
Endocrinology

ISSN: 0013-7227 1945-7170

Año de publicación: 2004

Volumen: 145

Número: 2

Páginas: 1011-1016

Tipo: Artículo

DOI: 10.1210/EN.2003-0652 GOOGLE SCHOLAR lock_openAcceso abierto editor

Otras publicaciones en: Endocrinology

Resumen

Polarized transport of newly synthesized proteins to the apical surface of epithelial cells takes place by a direct pathway from the Golgi or by an indirect route involving the delivery of the protein to the basolateral surface, followed by its endocytosis and transport across the cell. The indirect pathway, named transcytosis, is also used to translocate external material across the cell. MAL, a raft-associated integral membrane protein required for the direct apical route, is known to be expressed in the thyroid epithelium. MAL2, a member of the MAL protein family, has been recently identified as an essential component of the machinery for the transcytotic route inhuman hepatoma cells. Herein, we have investigated the expression and distribution of MAL2 in the human thyroid. MAL2 mRNA species were detected in the thyroid. Immunohistochemical analysis of thyroid follicles indicated that, in contrast to MAL, which predominantly distributed to the Golgi region, MAL2 distributed to the apical membrane. Biochemical analysis in primary thyrocyte cultures indicatedthat MAL2 exclusively resides in raft membranes. Confocal immunofluorescence analysis of thyrocyte cultures revealed that MAL2 predominantly localized in a subapical endosome compartment that was positive for Rab11a. Alterations in MAL2 expression, distribution, and appearance were found in specific types of follicular cell-derived carcinomas. Although the role of MAL2 has not been directly addressed in this study, the simultaneous expression of MAL and MAL2 suggests that traffic to the apical membrane in thyrocytes may rely on MAL for the direct route and on MAL2 for the transcytotic pathway

Información de financiación

This work was supported by grants from the Ministerio de Ciencia y Tecnología (PM99-0092; BMC2003-03297), the Comunidad de Madrid (08.5/0066.1/2001), Fondo de Investigacion Sanitaria (01/0085-01 and -02), and Fundacion Eugenio Rodriguez Pascual. An institutional grant from the Fundación Ramón Areces to Centro de Biología Molecular “Severo Ochoa” is also acknowledged.

Financiadores

  • Ministerio de Ciencia y Tecnología Spain
    • PM99-0092; BMC2003-03297
  • Comunidad de Madrid Spain
    • 08.5/0066.1/2001
  • Fondo de Investigación Sanitaria Spain
    • 01/0085-01 and -02

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