Alpha1beta1-integrin is an essential signal for neurite outgrowth induced by thrombospondin type 1 repeats of SCO-spondin.
In the central and peripheral nervous systems a heterogeneous group of proteins constituting the thrombospondin superfamily provides a cue for axonal pathfinding. They either contain or are devoid of the tripeptide RGD, and the sequence(s) and mechanism(s) which trigger in vitro their neurite-promoting activity have remained unclear. In this study, we reconsider the problem of whether sequences present in the thrombospondin type 1 repeats (TSRs), and independent of the well-known RGD-binding site, may activate integrins and account for their neurite-promoting activity. SCO-spondin is a newly identified member of the thrombospondin superfamily, which shows a multidomain organization with a great number of TSR motifs but no RGD sequence. Previous research has implicated oligopeptides derived from SCO-spondin TSRs in in-vitro development of various neuronal cell types. In this study, we investigate whether function-blocking antibodies directed against integrin subunits can block these effects in cell line B104, cloned from a neuroblastoma of the rat central nervous system. By two different approaches: flow cytometry revealing short-term effects and cell cultures revealing long-term effects, we show that: (a). activation of cell metabolism, (b). changes in cell size and structure, and (c). neurite-promoting activity induced by TSR oligopeptides are inhibited by function-blocking antibodies to beta1-subunit. Using a panel of function-blocking antibodies directed against various integrin alpha-subunits we show that the alpha1-subunit might be the partner of the beta1-subunit in B104 cells. Thus, we demonstrate that an original sequence within a TSR motif from SCO-spondin promotes neurite outgrowth through an intracellular signal driven by integrins, independently of an RGD-binding site.
Bamdad
M
M
Faculté de Médecine, UMR INSERM 384 et Laboratoire de Biochimie médicale, 28 place Henri-Dunant, BP 38, 63001, Clermont-Ferrand Cedex, France.
Volle
D
D
Dastugue
B
B
Meiniel
A
A
D000595:Amino Acid Sequence; D000818:Animals; D015816:Cell Adhesion Molecules, Neuronal / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D002999:Clone Cells; D039222:Integrin alpha1beta1 / Q000378:metabolism*; D016501:Neurites / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D009842:Oligopeptides / Q000378:metabolism; D010455:Peptides / Q000737:chemistry / Q000378:metabolism* / Q000494:pharmacology; D051381:Rats; D012091:Repetitive Sequences, Nucleic Acid; D015398:Signal Transduction; D019700:Thrombospondin 1 / Q000737:chemistry / Q000378:metabolism*
D015816:Cell Adhesion Molecules, Neuronal; D039222:Integrin alpha1beta1; D009842:Oligopeptides; D010455:Peptides; C108402:SCO-spondin; D019700:Thrombospondin 1; C047981:arginyl-glycyl-aspartic acid