Rationale: Fig. 3e,f,j PTPdelta colocalizes with VGLUT1 but not with VGAT in rat hippocampal neurons. PTPdelta colocalize with PSD-95 in CA1stratumradiatum of mouse brain.
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"PTPs immunoreactivity was also present in a punctate pattern decorating the dendrites of cultured hippocampal neurons at DIV 15 and these puncta overlapped with VGLUT1 (Figure 3E). PTPs puncta overlapping VGLUT1 were also observed on axons not contacting dendrites, suggesting an axonal localization (Figure 3E, arrowheads). PTPs puncta were not colocalized with VGAT clusters (Figure 3F). Furthermore, PTPs puncta were apposed to PSD-95 puncta in brain, as shown here for hippocampal CA1 region (Figure 3J). Thus, endogenous PTPs is also localized to excitatory synaptic sites in vitro and in vivo."
Fig.4 because PTPdelta interect with TrkC, the figure shows that TrkC and PTPs ectodomains, linked to beats, induce excitatory presynaptic and postsynaptic differentiation, respectively.
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To test whether PTPs mediates TrkC induced presynaptic differentiation, we investigated synapsin clustering around
TrkC-Fc-coated beads that contacted axons expressing either HA-PTPs or HA-PTPs lacking the intracellular domain
(HA-PTPsDICD). TrkC-Fc-coated beads induced HA-PTPs clustering accompanied by synapsin clustering on axons (Figures 4D and 4E). TrkC-induced synapsin clustering associated with HAPTPs was equivalent to TrkC-induced synapsin clustering on
neighboring nontransfected axons (Figure 4E), suggesting that
HA-PTPs is comparable in activity to the endogenous presynaptic
receptor of TrkC. In contrast, TrkC-Fc-coated beads that
induced HA-PTPsDICD clustering on axons did not induce simultaneous clustering of synapsin (Figures 4D and 4E). Presumably, HA-PTPsDICD effectively competed with endogenous PTPs for TrkC binding and blocked transmembrane signaling from TrkC to axonal intracellular targets for presynaptic differentiation. Taken together, these data suggest that PTPs is an axonal receptor for TrkC that triggers presynaptic differentiation.
Next, we tested whether PTPs ectodomain triggers excitatory
postsynaptic differentiation associated with dendritic accumulation of TrkC. PTPs-Fc-coated beads that contacted dendrites induced clustering of endogenous dendritic TrkC with NMDA receptor subunit NR1 (Figure 4F). NR1 clusters induced by
PTPs-Fc-coated beads were not apposed to synapsin (Figure
4G), indicating that these NR1 clusters were not associated with interneuronal synapses. PTPs-Fc-coated beads also induced clustering of PSD-95 but not of gephyrin (Figures 4H and 4I). We also confirmed in the coculture assay that COS cells expressing PTPs-CFP induced clustering of NR1 (data not shown) and of PSD-95 but not of gephyrin (Figure S4G) on contacting
dendrites. These data indicate that PTPs acts as a presynaptic factor to induce excitatory postsynaptic differentiation
and suggest that its postsynaptic receptor is TrkC."
7/11/2017 Pim
- Based on the known transmembrane topology of the protein, the "integral component of ... membrane" term was chosen.. Experimental description: 7/11/2017 Pim
- Species of cultured neurons is not explicitly stated in the paper.
- Species of intact tissue is of mouse
- Species of over expressed PTPs-ICD is mouse species: "and HA-PTP-ICD, the mature form of mouse PTP lacking aa 945-1501 was subcloned into spYFP-C1 and spHA-C1, respectively"
- I have chosen mouse species based on Fig.3J
Authors stated in personal communication:
PTPsigma-Fc is based on mouse PTPsigma (BC052462).
Re. neuronal cultures, we used rat primary hippocampal neuron cultures.
- I chose mouse species based on overexpressed protein.