Calcineurin and huntingtin form a calcium-sensing machinery that directs neurotrophic signals to the nucleus

Abstract

When a neurotrophin binds at the presynapse, it sends survival signals all the way to the nucleus on signaling endosomes. These endosomes fuel their own journey with on-board glycolysis-but how is that journey initiated and maintained? Using microfluidic devices and mice, we find that the calcium released upon brain-derived neurotrophic factor (BDNF) binding to its receptor, tropomyosin receptor kinase B (TrkB), is sensed by calcineurin on the cytosolic face of the endosome. Calcineurin dephosphorylates huntingtin, the BDNF scaffold, which sets the endosome moving in a retrograde direction. In an in vitro reconstituted microtubule transport system, controlled calcium uncaging prompts purified vesicles to move to the microtubule minus end. We observed similar retrograde waves of TrkA-and epidermal growth factor receptor (EGFR)-bearing endosomes. Signaling endosomes in neurons thus carry not only their own fuel, but their own navigational system. RESULTS CaN localizes on the surface of motile vesiclesWe used Thy1:p50-GFP mouse forebrains for our proteomic study (22-24), isolating vesicles that were immunopositive for p50-green

Huntingtin-KIF1A-mediated axonal transport of synaptic vesicle precursors influences synaptic transmission and motor skill learning in mice

“…The anterograde transport of SVP is driven predominantly by the kinesin-3 motor KIF1A (Guedes-Dias and Holzbaur, 2019). HTT and KIF1A interactomes suggested a possible interaction between the two proteins (Shirasaki et al, 2012;Stucchi et al, 2018), but HTT has not yet been shown to interact functionally with KIF1A. We observed KIF1A in the proteome of HTT-associated vesicles (Fig.…”

“…To investigate whether HTT and its phosphorylation affect the transport of SVP in a physiologically relevant system, we reconstituted mature corticostriatal circuits in microfluidic devices (Moutaux et al, 2018; Virlogeux et al, 2018). These devices have been used to establish HTT’s role in the transport of organelles such as BDNF-containing vesicles and signaling endosomes (Gauthier et al, 2004; Liot et al, 2013; Scaramuzzino et al, 2022; Virlogeux et al, 2018). Microfluidics consist of a presynaptic and a postsynaptic compartment containing cortical and striatal neurons, respectively, and a middle synaptic compartment that receives axons from cortical neurons and dendrites originating from striatal neurons ( Fig.…”

“…This work places HTT among the proteins that participate in SVP transport (Guedes-Dias and Holzbaur, 2019) and closes a loop opened by the discovery that DENN/MADD, a Rab3-GEP that binds to KIF1A (and KIF1Bß) regulates SVP binding to microtubules according to Rab3's nucleotide state (Niwa et al, 2008). Rab3 is part of the HTT interactome (Shirasaki et al, 2012) and enriched in SVs (Takamori et al, 2006); previous work in Drosophila larval axons showed that reducing HTT levels decreases the transport of Rab3-positive vesicles (White et al, 2015). In the context of Huntington's disease, both Rab3 levels and the conversion from GTP to GDP state are dysregulated, which is consistent with a role for HTT in the transport of SVPs.…”

Modulation of huntingtin degradation by cAMP-dependent protein kinase A (PKA) phosphorylation of C-HEAT domain Ser2550

“…Ser421 phosphorylation by AKT, and dephosphorylation by calcinurin, recruits and releases kinesin, respectively, thereby determining the direction of vesicle transport (e.g. BDNF) (Colin et al, 2008; Scaramuzzino, Cuoc, Pla, Humbert, & Saudou, 2022), while phosphorylation of this site is also reported to decrease huntingtin-cleavage and fragment-toxicity (Warby et al, 2005) and to influence mitochondrial phenotypes and toxicity in HD neuronal cells (Xu et al, 2020). CDK5 phosphorylation of pSer434 was associated with decreased caspase cleavage of huntingtin (Luo, Vacher, Davies, & Rubinsztein, 2005), whereas CDK5 phosphorylation of pSer1181 and pSer1201was reported to mediate huntingtin toxicity in neuronal cultures (Anne, Saudou, & Humbert, 2007).…”

Directed evolution of a bright variant of mCherry: Suppression of non-radiative decay by fluorescence lifetime selections

“…Despite its poor brightness, mCherry is a popular RFP for cellular sensing and imaging because of its widespread availability in a plethora of fusion constructs. 25,26 This monomeric RFP traces its lineage from the naturally occurring tetramer DsRed. 27 The consequent engineering strategies on DsRed resulted in a FP with high expression and fast chromophore maturation, low phototoxicity, and a favorable red-shift of absorption and emission spectra.…”