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

Abstract

Anterograde transport of brain-derived neurotrophic factor (BDNF) vesicles from the soma to neurite terminals is necessary for activity-dependent secretion of BDNF to mediate synaptic plasticity, memory and learning, and retrograde BDNF transport back to the soma for recycling. In our study, overexpression of the cytoplasmic tail of the carboxypeptidase E (CPE) found in BDNF vesicles significantly reduced localization of BDNF in neurites of hippocampal neurons. Live-cell imaging showed that the velocity and distance of movement of fluorescent protein-tagged CPE-or BDNFcontaining vesicles were reduced in both directions. In pull-down assays, the CPE tail interacted with dynactin along with kinesin-2 and kinesin-3, and cytoplasmic dynein. Competition assays using a CPE tail peptide verified specific interaction between the CPE tail and dynactin. Thus, the CPE cytoplasmic tail binds dynactin that recruits kinesins or dynein for driving bi-directional transport of BDNF vesicle to maintain vesicle homeostasis and secretion in hippocampal neurons.

Amyloid- Peptide Oligomers Disrupt Axonal Transport through an NMDA Receptor-Dependent Mechanism That Is Mediated by Glycogen Synthase Kinase 3 in Primary Cultured Hippocampal Neurons

“…The impairment is higher for anterograde transport, with possible consequences in the distribution of organelles to distal portions of the cell, e.g., synapses. Although the motor for DCV transport has not been clearly identified in mammalian neurons, it appears likely that A␤Os preferentially disrupt a plus-end motor, possibly KIF1A (Park et al, 2008). Whether KIF1A is regulated by GSK-3␤ is yet to be determined.…”

“…To answer this question, we measured protein levels of the motor protein dynein, the primary motor for retrograde transport, and of the anterograde kinesins, KIF1A, KIF5A, and KIF5C, motors implicated in the transport of DCVs and/or mitochondria (Hirokawa and Noda, 2008;Park et al, 2008), as well as total tubulin levels. Treatment with A␤Os for 18 h did not modify the total level of tubulin or any of the motor proteins investigated, eliminating the possibility that axonal transport defects could be caused by protein degradation (Fig.…”

Obese carboxypeptidase E knockout mice exhibit multiple defects in peptide hormone processing contributing to low bone mineral density

“…In addition to its enzymatic function, CPE has been shown to facilitate trafficking of several prohormones into the granules of the RSP (10, 26). Recently, live-cell imaging and coimmunoprecipitation studies demonstrated a role for its cytoplasmic carboxyl terminus in the transport of peptidergic vesicles via interaction with dynactin, an anterograde microtubule-based motor protein complex (27,28). The involvement of CPE in multiple cellular functions would suggest that deficiencies in CPE would lead to many pathologies.…”

Can an increase in neuropeptide production in the soma lead to DCV circulation in axon terminals with type III en passant boutons?

“…what smaller values of 0.625 and 0.628 μm/s for the average antero-37 grade and retrograde DCV velocities, respectively, are reported in de 38 Jong et al [22]. Even smaller values of 0.34 and 0.41 μm/s for the av-39 erage anterograde and retrograde DCV velocities are reported in Park 40 et al [23]. We will use a value of 1 μm/s for our estimates.…”

“…A more precise value for T 1/2,ax can be easily incorporated into our model once experimental data are available. d The range of v is 0.34-1.27 μm/s, which is based on various measurements of the average DCV velocity reported in Wong et al [20], Kwinter et al [19], de Jong et al [22], and Park et al [23]. We used a value of 1 μm/s as an estimate for v. e A value of 0.1 for for type Ib boutons is based on Wong et al [20], an increased value of 0.4 for the most distal type Ib bouton was first suggested in Kuznetsov and Kuznetsov [30] to simulate the initial DCV accumulation in the most distal bouton.…”