Dystrophin isoform Dp71 is present in lamellipodia and focal complexes in human astrocytoma cells U-373 MG Carlos G. García-Tovar 1,4 , José Luna 2 , Raúl Mena 2 , Carlos I. Soto-Zárate 1,4 , Rafael Cortés 1 , Armando Pérez 1 , Gloria León-Avila 3 , Dominique Mornet 5 , Alvaro Rendón 6 , and José Manuel Hernández 1 * Departments of 1 Cell Biology, 2 Physiology, Biophysics and Neurosciences, and 3 Genetics and Molecular Biology, CINVESTAV-IPN, Zacatenco, México, 4 Morphology Unit, FES-Cuautitlán, Cuautitlán Izcalli, México, 5 INSERM U 128, IFR 24, Montpellier, France, and 6 INSERM EMI 99-18, Strasbourg, France Received 25 February 2002 and in revised form 5 June 2002 and 4 July 2002; accepted 4 July 2002 Summary Dp71 is the most abundant product of the dmd gene in the brain. There are at least 2 isoforms derived from alternative splicing of exon 78 (Dp71d, which contains exon 78 and Dp71f, the spliced isoform) but the precise localization and function of each isoform is still unknown. In the present study, we demonstrate by RT-PCR that the Dp71f isoform is present in an astrocytoma cell line U-373 MG, and its subcellular localization was determined in the cytoplasm, particularly in perinuclear areas, with lower amounts towards the periphery but increasing in the leader borders of lamellipodia and focal complexes. Double labeling indirect immunofluorescence showed that Dp71f colocalized with actin-like β-dystro- glycan and β-1 integrin. We also demonstrated by triple labeling that Dp71f was colocalized with actin and two members of integrin complexes, α-actinin and vinculin, in focal complexes. Ventral plasma membranes were enriched and in those containing focal complex proteins, we found colocalization of Dp71f, actin and vinculin. It is concluded that U-373 MG cells express Dp71f as part of lamellipodia and focal complex proteins, and possibly connected via distroglycan complexes to integrin complexes. Key words: Dp71f – dystrophin – glycoprotein complex – integrin complex – cell adhesion 0065-1281/02/104/03-245 $ 15.00/0 Introduction Dystrophin (Dp427) is the largest member of the spec- trin superfamily, one known function of which is to bind membrane glycoproteins and cytoplasmic proteins, including their link with the actin network and sig- nalling molecules to regulate actin interactions (Hartwig, 1994). Dp is located on the subsarcolemmal surface in skeletal muscle. Dp is an actin-binding pro- tein (Levine et al., 1992; Rybakova et al., 1996) associ- ated with 2 other proteins: dystroglycans and sarcogly- cans-sarcospan, also called dystrophin-associated gly- coproteins (DAGs) to form the dystrophin-DAG com- plex (DGC; Crosbie et al., 1997; Yoshida et al., 2000), which also interacts with syntrophins-dystrobrevin complexes. Dystrophin interacts directly with the dys- troglycan subcomplex which binds to laminin. Thus, dystrophin and dystroglycans form a link between the extracellular matrix and the actin network (Ervasti et al., 1990; Ervasti and Campbell, 1991, 1993; Susuki et al., *Correspondence to: Dr. José Manuel Hernández Hernández, Departamento de Biología Celular, Centro de Investigación y de Estudios Avan- zados del I.P.N.,Av. I.P.N. 2508, Col. San Pedro Zacatenco, México, CP 07360; tel: *52 55 57473800; ext. 3989; fax: *52 55 57477081; e-mail: manolo@cell.cinvestav.mx acta histochem. 104(3) 245–254 (2002) © Urban & Fischer Verlag http://www.urbanfischer.de/journals/actahist