Truncated TrkB mediates the endocytosis and release of BDNF and neurotrophin-4/5 by rat astrocytes and Schwann cells in vitro

Binding and cross-linking studies with radiolabeled neurotrophins demonstra te that cultured rat hippocampal astrocytes lack full-length TrkB, but do e xpress high levels of truncated TrkB (tTrkB). In astrocytes and Schwann cel ls, tTrkB appears to have the novel function of mediating the endocytosis o f neurotrophins into an acid-stable, Triton X-100 resistant intracellular p ool that is released back into the medium in a temperature-dependent manner . Chloroquine treatment, trichloroacetic acid solubility, and sodium dodecy l sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis revealed that when incubated with astrocytes or Schwann cells for at least 48 h neit her the intracellular nor the released neurotrophins were significantly deg raded. The endocytosis and release of neurotrophins may represent a novel m echanism whereby neuroglia can regulate the local concentration of these ne urotrophic factors for extended periods of time. (C) 2000 Elsevier Science B.V. All rights reserved.