title: Selective increase in the binding of the alpha 1 beta 1 integrin for collagen type IV during neurite outgrowth of human neuroblastoma TR 14 cells.
abstract: Regulation of beta 1 integrins in neurite outgrowth following N6,2'-O-dibutyryladenosine 3':5'-cyclic monophosphate (dBcAMP) treatment was investigated using the human neuroblastoma cell line TR 14. Three beta 1 integrins were identified: the alpha 1 beta 1 receptor bound collagen type I, collagen type IV and probably laminin; the alpha 2 beta 1 integrin bound collagen type I; and the alpha v beta i receptor bound fibronectin. Neurite extension was detectable as early as 30 minutes following dBcAMP treatment, was maximal after 24 hours and remained constant during treatment for 4 days. Adhesion-perturbing beta 1 subunit-specific antibodies, added together with dBcAMP, prevented the outgrowth of new neurites. During the first 24 hours of neurite outgrowth, no change was observed in the amount of beta 1 integrins nor in their topographic distribution. However, dBcAMP treatment increased the binding of alpha 1 beta 1 receptors to collagen type IV-Sepharose by a factor 2.3 +/- 0.6 (P < 0.02), while no alteration in the binding to collagen type I was detected. Moreover, neurites and growth cones were immunoreactive for collagen type IV but not for collagen type I. Consistently dBcAMP-induced neurite outgrowth was inhibited by adhesion-perturbing alpha 1 subunit-specific antibodies. Following maximal neurite outgrowth, the amount of beta 1 integrins determined by immunoprecipitation and by confocal microscopy decreased to 58.3 +/- 11.2% (P < 0.001) and to 55.4 +/- 17.5% (P < 0.001) of untreated levels, respectively, without any change in the level of beta 1 mRNA or de novo synthesized beta 1 precursor. However, pulse-chase experiments showed an increased turnover of the beta 1 subunit: the amount of beta 1 precursor that was degraded after 1 hour chase was 50.5 +/- 8.4% in cells treated for 4 days and 34.2 +/- 3.9% in untreated cells (P < 0.02); the amount of mature beta 1 after 24 hours chase was smaller in cells treated for 4 days compared to untreated cells. In conclusion, during neurite outgrowth, alpha 1 beta 1 integrins are required and acquire an enhanced binding activity for collagen type IV; but following maximal neurite outgrowth, expression of beta 1 integrins is reduced.
authors.affiliation: Center for Human Genetics, University of Leuven, Belgium.
authors.forename: G
authors.initials: G
authors.lastname: Carmeliet
authors.forename: B
authors.initials: B
authors.lastname: Himpens
authors.forename: J J
authors.initials: JJ
authors.lastname: Cassiman
mesh_terms: D015703:Antigens, CD / Q000378:metabolism; D003994:Bucladesine / Q000494:pharmacology; D002451:Cell Compartmentation; D003094:Collagen / Q000378:metabolism*; D005353:Fibronectins / Q000378:metabolism; D005455:Fluorescent Antibody Technique; D006801:Humans; D039222:Integrin alpha1beta1; D019012:Integrin beta1; D016023:Integrins / Q000145:classification / Q000378:metabolism*; D007797:Laminin / Q000378:metabolism; D018613:Microscopy, Confocal; D009420:Nervous System / Q000166:cytology / Q000187:drug effects / Q000254:growth & development; D016501:Neurites / Q000378:metabolism*; D009447:Neuroblastoma; D011233:Precipitin Tests; D011485:Protein Binding; D017469:Receptors, Fibronectin; D014407:Tumor Cells, Cultured
chemical_list: D015703:Antigens, CD; D005353:Fibronectins; D039222:Integrin alpha1beta1; D019012:Integrin beta1; D016023:Integrins; D007797:Laminin; D017469:Receptors, Fibronectin; D003994:Bucladesine; D003094:Collagen