Distribution of GAP-43, beta-III tubulin and F-actin in developing and regenerating axons and their growth cones in vitro, following neurotrophin treatment.
Brain derived neurotrophic factor (BDNF) when added to explant cultures of both embryonic and adult retinal ganglion cell (RGC) axons exerted a marked effect on their growth cone size and complexity and also on the intensity of GAP-43, beta-III tubulin and F-actin immunoreaction product in their axons. GAP-43 was distributed in axons, lamellipodia, and filopodia whereas beta-III tubulin was distributed along the length of developing and adult regenerating axons and also in the C-domain of their growth cones. BDNF-treated developing RGC growth cones were larger and displayed increased numbers of GAP-43 and microtubule-containing branches. Although filopodia and lamellipodia were lost from both developing and adult RGC growth cones following trkB-IgG treatment, the intensity of the immunoreaction product of all these molecules was reduced and trkB-IgGs had no effect on the axonal distribution of betas-III tubulin and GAP-43. BDNF-treated growth cones also displayed increased numbers of F-actin containing filopodia and axonal protrusions. This study demonstrates, for the first time, that trkB-IgG treatment causes the loss of F-actin in the P-domain of growth cone tips in developing and regenerating RGC axons. Although microtubules and F-actin domains normally remained distinct in cultured growth cones, beta-III tubulin and F-actin overlapped within the growth cone C-domain, and within axonal protrusions of adult RGC axons, under higher concentrations of BDNF. The collapse of RGC growth cones appeared to correlate with the loss of F-actin. In vitro, trkB signalling may therefore be involved in the maintenance and stabilisation of RGC axons, by influencing F-actin polymerisation, stabilisation and distribution.
Avwenagha
Ovokeloye
O
Department of Anatomy and Developmental Biology, University College London, WC1E 6BT.
Campbell
Gregor
G
Bird
Margaret M
MM
D008841:Actin Cytoskeleton / Q000187:drug effects / Q000378:metabolism; D000199:Actins / Q000187:drug effects / Q000378:metabolism*; D000818:Animals; D001369:Axons / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D019208:Brain-Derived Neurotrophic Factor / Q000378:metabolism / Q000494:pharmacology; D005333:Fetus; D019922:GAP-43 Protein / Q000187:drug effects / Q000378:metabolism*; D020439:Growth Cones / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D007074:Immunoglobulin G / Q000378:metabolism / Q000494:pharmacology; D008870:Microtubules / Q000187:drug effects / Q000378:metabolism; D009414:Nerve Growth Factors / Q000494:pharmacology*; D009416:Nerve Regeneration / Q000187:drug effects / Q000502:physiology; D009419:Nerve Tissue Proteins / Q000187:drug effects / Q000378:metabolism; D009924:Organ Culture Techniques; D011554:Pseudopodia / Q000187:drug effects / Q000378:metabolism / Q000648:ultrastructure; D051381:Rats; D017208:Rats, Wistar; D020813:Receptor, trkB / Q000187:drug effects / Q000378:metabolism; D012160:Retina / Q000166:cytology / Q000196:embryology / Q000254:growth & development; D012165:Retinal Ganglion Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D014404:Tubulin / Q000187:drug effects / Q000378:metabolism*; D015854:Up-Regulation / Q000187:drug effects / Q000502:physiology
D000199:Actins; D019208:Brain-Derived Neurotrophic Factor; D019922:GAP-43 Protein; D007074:Immunoglobulin G; D009414:Nerve Growth Factors; D009419:Nerve Tissue Proteins; C488416:Tubb3 protein, rat; D014404:Tubulin; C462941:beta3 tubulin, mouse; D020813:Receptor, trkB