Mapping CRMP3 domains involved in dendrite morphogenesis and voltage-gated calcium channel regulation

Abstract

SummaryAlthough hippocampal neurons are well-distinguished by the morphological characteristics of their dendrites and their structural plasticity, the mechanisms involved in regulating their neurite initiation, dendrite growth, network formation and remodeling are still largely unknown, in part because the key molecules involved remain elusive. Identifying new dendrite-active cues could uncover unknown molecular mechanisms that would add significant understanding to the field and possibly lead to the development of novel neuroprotective therapy because these neurons are impaired in many neuropsychiatric disorders. In our previous studies, we deleted the gene encoding CRMP3 in mice and identified the protein as a new endogenous signaling molecule that shapes diverse features of the hippocampal pyramidal dendrites without affecting axon morphology. We also found that CRMP3 protects dendrites against dystrophy induced by prion peptide PrP . Here, we report that CRMP3 has a profound influence on neurite initiation and dendrite growth of hippocampal neurons in vitro. Our deletional mapping revealed that the C-terminus of CRMP3 probably harbors its dendritogenic capacity and supports an active transport mechanism. By contrast, overexpression of the C-terminal truncated CRMP3 phenocopied the effect of CRMP3 gene deletion with inhibition of neurite initiation or decrease in dendrite complexity, depending on the stage of cell development. In addition, this mutant inhibited the activity of CRMP3, in a similar manner to siRNA. Voltage-gated calcium channel inhibitors prevented CRMP3-induced dendritic growth and somatic Ca 2+ influx in CRMP3-overexpressing neurons was augmented largely via L-type channels. These results support a link between CRMP3-mediated Ca 2+ influx and CRMP3-mediated dendritic growth in hippocampal neurons.

CRMPs: critical molecules for neurite morphogenesis and neuropsychiatric diseases

“…In cortical neurons, Ena/VASP deletion also prevents neurite initiation but by inhibiting filopodia formation, 33 the second step in establishing the primary neurites. The correlation between levels of CRMP3 expression, dendrite/spine morphogenesis and the activation of L-and N-type VGCCs by CRMP3 provide strong support for an inductive role of CRMP3 in neurite initiation and dendritic development and plasticity, at least partly via Ca 2+ influx 29 (Figure 1d). In contrast, CRMP5 depletion by RNA interference enhances the length and number of neurites, whereas its overexpression induces mitophagy and reduces dendritic length.…”

“…43 In CRMP1 − / − mice, axonal lengths in cerebellar explant cultures are not altered, 44 suggesting selective functional activity of CRMP1 depending on cell types and/or species. Finally, despite their role in dendritogenesis, overexpression or deletion of CRMP3 in cultured hippocampal CA1 neurons 29 and deletion of CRMP5 in cerebellar explant cultures 36 yield no apparent alteration of axon morphology, suggesting that some CRMPs may affect only dendrites.…”

“…Although neurons from control wild type and CRMP3+/ − mice polarize and grow normally, all neurons lacking CRMP3, identified by their expression of the LacZreporter gene (SI-A), from CRMP3 − / − littermates do not initiate neurite formation. 29 They remain spherical, even after 10 days in vitro. This defect in neuritogenesis is largely due to a failure to evolve from stage 1 to stage 2, defined as neurite initiation.…”

CRMPs Function in Neurons and Glial Cells: Potential Therapeutic Targets for Neurodegenerative Diseases and CNS Injury

“…The roles of CRMP3 and CRMP5 in changing the morphology of axons have not yet been reported [26,89]. In contrast, high homology is reported between CRMP1, CRMP2, and CRMP4, where both have the inhibitory signaling and kinases described earlier downstream.…”

“…Consistent with this, our studies have shown that Crmp2KI/KI mice exhibits remarkable nociceptive recovery after SCI, and no significant difference was observed in the hot plate test latencies (sensitivity to thermal nociception) between intact and injured Crmp2KI/KI mice after SCI [42], suggesting an absence of abnormal hypersensitivity in the Crmp2KI/KI mice after spinal cord transection. Although in vitro studies have shown that the calcium influx via L-type Ca 2+ channels is required for CRMP3-induced dendritic arbor [89], the relationships between other CRMPs and CaV2.2 on physiological functions in vivo are largely unknown.…”