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J. Biol. Chem., Vol. 283, Issue 36, 24760-24769, September 5, 2008

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Cib2 Binds Integrin 7Bβ1D and Is Reduced in Laminin 2 Chain-deficient Muscular Dystrophy^*

Mattias Häger, Maria Giulia Bigotti¹, Renata Meszaros¹, Virginie Carmignac¹, Johan Holmberg, Valérie Allamand^¶||, Mikael Åkerlund, Sebastian Kalamajski, Andrea Brancaccio^**, Ulrike Mayer, and Madeleine Durbeej²

From the Department of Experimental Medical Science, Division for Cell and Matrix Biology, University of Lund, 221 84 Lund, Sweden, Department of Biochemistry, University of Rome La Sapienza, 00185 Rome, Italy, ^¶INSERM U582, 75651 Paris, France, ^||Institut de Myologie, IFR14, Université Pierre et Marie Curie-Paris 6, UMR-S582, 75250 Paris, France, ^**Istituto di Chimica del Riconoscimento Molecolare, c/o Istituto di Biochimica e Biochimica Clinica, Università Cattolica del Sacro Cuore, 00168 Rome, Italy, and School of Biological Sciences, University of East Anglia, Norwich NR4 7TJ, United Kingdom

Mutations in the gene encoding laminin 2 chain cause congenital muscular dystrophy type 1A. In skeletal muscle, laminin 2 chain binds at least two receptor complexes: the dystrophin-glycoprotein complex and integrin 7β1. To gain insight into the molecular mechanisms underlying this disorder, we performed gene expression profiling of laminin 2 chain-deficient mouse limb muscle. One of the down-regulated genes encodes a protein called Cib2 (calcium- and integrin-binding protein 2) whose expression and function is unknown. However, the closely related Cib1 has been reported to bind integrin IIb and may be involved in outside-in-signaling in platelets. Since Cib2 might be a novel integrin 7β1-binding protein in muscle, we have studied Cib2 expression in the developing and adult mouse. Cib2 mRNA is mainly expressed in the developing central nervous system and in developing and adult skeletal muscle. In skeletal muscle, Cib2 colocalizes with the integrin 7B subunit at the sarcolemma and at the neuromuscular and myotendinous junctions. Finally, we demonstrate that Cib2 is a calcium-binding protein that interacts with integrin 7Bβ1D. Thus, our data suggest a role for Cib2 as a cytoplasmic effector of integrin 7Bβ1D signaling in skeletal muscle.

Received for publication, February 12, 2008 , and in revised form, June 10, 2008.

^* This work was supported by grants from the Muscular Dystrophy Association and Association Française contre les Myopathies (to M. D.) and by the Wenner-Gren Foundations (to V. C.). The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

The on-line version of this article (available at http://www.jbc.org) contains supplemental Figs. 1–3.

¹ These authors contributed equally to this work.

² To whom all correspondence should be addressed: University of Lund, Dept. of Experimental Medical Science, Division for Cell and Matrix Biology, BMC B12, 221 84 Lund, Sweden. Tel.: 46-46-222-08-12; Fax: 46-46-222-08-55; E-mail: madeleine.durbeej-hjalt{at}med.lu.se.

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