Tài liệu Báo cáo khoa học: Cell surface nucleolin on developing muscle is a potential ligand for the

Cell surface nucleolin on developing muscle is a potential

ligand for the axonal receptor protein tyrosine

phosphatase-r

Daniel E. Alete1

, Mark E. Weeks2

, Ara G. Hovanession3

, Muhamed Hawadle1 and

Andrew W. Stoker1

1 Neural Development Unit, Institute of Child Health, University College London, UK

2 Molecular Oncology, CRUK, Barts and The London School of Medicine and Dentistry, John Vane Centre, UK

3 UPR 2228 CNRS, UFR Biomedicale-Universite Rene Descartes, Paris, France

Vertebrate nervous system development relies on a

multitude of guidance cues to stimulate axonal exten￾sion and stable synaptic contacts with targets such as

muscles. Interpretation of these environmental signals

by growth cones involves multiple receptor classes such

as cell adhesion molecules (CAMs) [1], DCC and neu￾Keywords

affinity chromatography; axon targeting;

nucleolin; RAP assay; receptor protein

tyrosine phosphatases

Correspondence

A. W. Stoker, Neural Development Unit,

Institute of Child Health, University College

London, 30 Guilford Street, London WC1N

1EH, UK

Fax: +44 207 78314366

Tel: +44 207 9052244

E-mail: [email protected]

(Received 21 April 2006, revised 2 August

2006, accepted 15 August 2006)

doi:10.1111/j.1742-4658.2006.05471.x

Reversible tyrosine phosphorylation, catalyzed by receptor tyrosine kinases

and receptor tyrosine phosphatases, plays an essential part in cell signaling

during axonal development. Receptor protein tyrosine phosphatase-r has

been implicated in the growth, guidance and repair of retinal axons. This

phosphatase has also been implicated in motor axon growth and innerva￾tion. Insect orthologs of receptor protein tyrosine phosphatase-r are also

implicated in the recognition of muscle target cells. A potential extracellu￾lar ligand for vertebrate receptor protein tyrosine phosphatase-r has been

previously localized in developing skeletal muscle. The identity of this mus￾cle ligand is currently unknown, but it appears to be unrelated to the hepa￾ran sulfate ligands of receptor protein tyrosine phosphatase-r. In this

study, we have used affinity chromatography and tandem MS to identify

nucleolin as a binding partner for receptor protein tyrosine phosphatase-r

in skeletal muscle tissue. Nucleolin, both from tissue lysates and in purified

form, binds to receptor protein tyrosine phosphatase-r ectodomains. Its

expression pattern also overlaps with that of the receptor protein tyrosine

phosphatase-r-binding partner previously localized in muscle, and nucleo￾lin can also be found in retinal basement membranes. We demonstrate that

a significant amount of muscle-associated nucleolin is present on the cell

surface of developing myotubes, and that two nucleolin-binding compo￾nents, lactoferrin and the HB-19 peptide, can block the interaction of

receptor protein tyrosine phosphatase-r ectodomains with muscle and ret￾inal basement membranes in tissue sections. These data suggest that muscle

cell surface-associated nucleolin represents at least part of the muscle bind￾ing site for axonal receptor protein tyrosine phosphatase-r and that nucle￾olin may also be a necessary component of basement membrane binding

sites of receptor protein tyrosine phosphatase-r.

Abbreviations

AP, alkaline phosphatase; CAM, cell adhesion molecule; FGF, fibroblast growth factor; FITC, fluorescein isothiocyanate; HB-19,

5[Kw(CH2N)PR]-TASP; HSPG, heparin sulfate proteoglycan; PLAP, placental alkaline phosphatase; PTP, protein tyrosine phosphatase; RAP,

receptor affinity probe; RPTP, receptor protein tyrosine phosphatase; RTK, receptor protein tyrosine kinase.

4668 FEBS Journal 273 (2006) 4668–4681 ª 2006 The Authors Journal compilation ª 2006 FEBS