Sorting and Activity-Dependent Secretion of BDNF Require Interaction of a Specific Motif with the Sorting Receptor Carboxypeptidase E

Abstract

Activity-dependent secretion of BDNF is important in mediating synaptic plasticity, but how it is achieved is unclear. Here we uncover a sorting motif receptor-mediated mechanism for regulated secretion of BDNF. X-ray crystal structure analysis revealed a putative sorting motif, I(16)E(18)I(105)D(106), in BDNF, which when mutated at the acidic residues resulted in missorting of proBDNF to the constitutive pathway in AtT-20 cells. A V20E mutation to complete a similar motif in NGF redirected a significant proportion of it from the constitutive to the regulated pathway. Modeling and binding studies showed interaction of the acidic residues in the BDNF motif with two basic residues in the sorting receptor, carboxypeptidase E (CPE). (35)S labeling experiments demonstrated that activity-dependent secretion of BDNF from cortical neurons was obliterated in CPE knockout mice. Thus, we have identified a mechanism whereby a specific motif I(16)E(18)I(105)D(106) interacts with CPE to sort proBDNF into regulated pathway vesicles for activity-dependent secretion.

Single-Cell Characterization of Retrograde Signaling by Brain-Derived Neurotrophic Factor

“…The mechanisms of this release are gradually being better understood as the molecular interactions responsible for regulated release are identified (Chen et al, 2005;Lou et al, 2005), but numerous functional issues remain to be clarified. In particular, it will be important to examine the relative roles of anterograde and retrograde BDNF signaling, both of which unequivocally occur but which may have different stimulus selectivities and functional outcomes.…”

A bi-directional carboxypeptidase E-driven transport mechanism controls BDNF vesicle homeostasis in hippocampal neurons

“…Carboxypeptidase E (CPE) is a proneuropeptide/prohormone processing enzyme (Fricker and Snyder, 1982;Hook and Loh, 1984) and is associated with BDNF vesicles in hippocampal and cortical neurons (Lou et al, 2005). The luminal domain of the membrane form of CPE acts as a sorting receptor for targeting BDNF to the regulated secretory pathway vesicles in hippocampal and cortical neurons (Lou et al 2005).…”

“…The luminal domain of the membrane form of CPE acts as a sorting receptor for targeting BDNF to the regulated secretory pathway vesicles in hippocampal and cortical neurons (Lou et al 2005). Membrane CPE can also exist in vesicles as a transmembrane protein with a cytoplasmic tail of ~10 amino acids at the C-terminus (Arnaoutova et al, 2003;Dhanvantari et al, 2002;Wu et al, 2004).…”

Sorting of growth hormone–erythropoietin fusion proteins in rat salivary glands

“…For example, in endocrine cells, sorting motifs of pro-opiomelanocortin (POMC), brain derived neurotrophic factor and proinsulin were shown to interact with membrane carboxypeptidase E, which acts as a sorting or retention receptor to target these prohormones to the RSP [31]. hGH contains a highly conserved C terminus domain that is similar to the RSP sorting domain of POMC.…”