Identification of Protein Tyrosine Phosphatase Receptor Type O (PTPRO) as a Synaptic Adhesion Molecule that Promotes Synapse Formation

Abstract

The proper formation of synapses-specialized unitary structures formed between two neurons-is critical to mediating information flow in the brain. Synaptic cell adhesion molecules (CAMs) are thought to participate in the initiation of the synapse formation process. However, functional analysis demonstrates that most well known synaptic CAMs regulate synaptic maturation and plasticity rather than synapse formation, suggesting that either CAMs work synergistically in the process of forming synapses or more CAMs remain to be found. By screening for unknown CAMs using a co-culture system, we revealed that protein tyrosine phosphatase receptor type O (PTPRO) is a potent CAM that induces the formation of artificial synapse clusters in co-cultures of human embryonic kidney 293 cells and hippocampal neurons cultured from newborn mice regardless of gender. PTPRO was enriched in the mouse brain and localized to postsynaptic sites at excitatory synapses. The overexpression of PTPRO in cultured hippocampal neurons increased the number of synapses and the frequency of miniature EPSCs (mEPSCs). The knock-down (KD) of PTPRO expression in cultured neurons by short hairpin RNA (shRNA) reduced the number of synapses and the frequencies of the mEPSCs. The effects of shRNA KD were rescued by expressing either full-length PTPRO or a truncated PTPRO lacking the cytoplasmic domain. Consistent with these results, the N-terminal extracellular domain of PTPRO was required for its synaptogenic activity in the co-culture assay. Our data show that PTPRO is a synaptic CAM that serves as a potent initiator of the formation of excitatory synapses. The formation of synapses is critical for the brain to execute its function and synaptic cell adhesion molecules (CAMs) play essential roles in initiating the formation of synapses. By screening for unknown CAMs using a co-culture system, we revealed that protein tyrosine phosphatase receptor type O (PTPRO) is a potent CAM that induces the formation of artificial synapse clusters. Using loss-of-function and gain-of-function approaches, we show that PTPRO promotes the formation of excitatory synapses. The N-terminal extracellular domain of PTPRO was required for its synaptogenic activity in cultured hippocampal neurons and the co-culture assay. Together, our data show that PTPRO is a synaptic CAM that serves as a potent initiator of synapse formation.

TRAF6 controls spinogenesis instructing synapse density and neuronal activity through binding neuroplastin

“…Thus, it has been considered that still unexplored molecular machineries interplaying with CAMs may promote synapse formation (Yoshihara et al, 2009;Jiang et al, 2017;Jang et al, 2017;Südhof 2017). Independent of their adhesive properties some CAMs can form transmembrane complexes in cis that in turn can recruit intracellular proteins and activate signaling mechanisms underlying neuronal development (Cavallaro and Dejana, 2011;Jang et al, 2017).…”

“…Using the ELM database (http://elm.eu.org/) we identified a single TRAF6 binding motif in the cytoplasmic tail of all neuroplastins from human, rat, and mouse ( Figure 2A) which fully matches the well-characterized TRAF6 binding motif (Ye at al., 2002;Sorrentino et al, 2008;Yin et al, 2009). Very surprisingly, the TRAF6 binding motif was not found amount a number of other known spinogenic type-1 CAMs namely N-Cadherin (Bozdagi et al, 2010), LRRTM (Linhoff et al, 2009), neuroligins (Varoqueaux et al, 2006), neurexins (Missler et al;2003), SynCAM1 (Robbins et al, 2010), EphB2 (Henderson et al, 2001), PTPR0 (Jiang et al, 2017), and others ( Figure S1). These results highlight both the specificity and novelty of the association of TRAF6 to neuroplastin to mediate spinogenesis.…”

An Excitatory Neural Assembly Encodes Short-Term Memory in the Prefrontal Cortex

“…All statistical analyses were performed using GraphPad Prism software (Jiang et al, 2017;Wei et al, 2016). The data are presented as the mean ± SEM.…”

Efficient implementation of convolutional neural networks in the data processing of two-photon in vivo imaging

“…All imaging experiments were performed as previously reported (Jiang et al , 2017; Su et al , 2016; Tian et al , 2018; Wei et al , 2016). A detailed description of the methods is available at Bioinformatics online.…”