Backbone resonance assignment of the pentraxin domain of the neuronal pentraxin receptor (NPTXR)

Interaction of the N-Terminal Domain of the AMPA Receptor GluR4 Subunit with the Neuronal Pentraxin NP1 Mediates GluR4 Synaptic Recruitment

Neuronal pentraxins comprise three neuronal proteins, neuronal pentraxin receptor (NPR) which is a type-II transmembrane protein on the neuronal surface, and secreted neuronal pentraxin-1 and NARP. The general functions of neuronal pentraxins at synapses have not been explored, except for their basic AMPAR binding properties. Here, we examined the functional role of NPR at synapses because it is the only neuronal pentraxin that is anchored to the neuronal cell-surface membrane. We find that NPR is a potent inducer of both excitatory and inhibitory heterologous synapses, and that knockdown of NPR in cultured neurons decreases the density of both excitatory and inhibitory synapses. Our data suggest that NPR performs a general, previously unrecognized function as a universal organizer of synapses.

e15022 Background: The human neuronal pentraxin receptor (NPTXR) gene encodes a type II transmembrane protein that functions as a trans-synaptic organizer and anchors neuronal pentraxin complexes to plasma membranes. Beside a subset of neuronal cells (Hippocampus and Cerebral Cortex), expression of NPTXR is not detected in all other tissues [ The Human Protein Atlas database]. In recent studies [Kanda et al. (2020) Mol. Cancer. doi: 10.1186/s12943-020-01251-0], transcriptome and bioinformatics analysis of gastric cancer (GC) tissues from patients with or without metastasis have revealed that NPTXR expression was associated with disease progression. NPTXR expression was also correlated negatively with survival in GC patients. It appears that NPTXR does not have a major physiological function; e.g., NPTXR−/− mice showed no abnormalities in reproduction, development, metabolism, or motor function. NPTXR is expressed in a number of GI cancers, i.e., gastric, esophageal, colorectal, pancreatic, bladder, liver, as well as breast and thyroid cancer. YB-800 is a fully humanized monoclonal antibody against NPTXR (identified by in silico analysis). Methods: The present studies were conducted to provide a rationale for the design of a YB-800-based antibody drug conjugate (ADC) for therapeutic intervention in oncology. Hence, YB-800 binding to and internalization in selected tumor cells, as well as immunohistochemistry (IHC) in tumor biopsies, were evaluated. Results: Taken together experimental data confirm that: (i) YB-800 binds to a new target (NPTXR) on selected tumor cells; confirmed by FACS analysis; (ii) IHC analysis in tumor samples demonstrates specific immunoreaction in bladder, gastric, prostate, hepatocellular carcinoma, colorectal cancer and cervical cancer, but not in adjacent healthy tissues; and (iii) once YB-800 binds to NPTXR, the conjugate is internalized in selected tumor cells in a time-dependent manner. Conclusions: In conclusion, YB-800 represents a first in class ADC candidate that could be used as novel treatment for gastro-intestinal cancers. Hence, as initial proof of concept, tesirine (DNA intercalating agent) and deruxtecan (topoisomerase I inhibitor) containing protease-sensitive linkers were coupled to YB-800 by stochastic maleimide conjugations to interchain cysteines. Initial results with YB-800-based ADCs will be discussed.

We have identified the first putative integral membrane pentraxin and named it neuronal pentraxin receptor (NPR). NPR is enriched by affinity chromatography on columns of a snake venom toxin, taipoxin, and columns of the taipoxin-binding proteins neuronal pentraxin 1 (NP1), neuronal pentraxin 2 (NP2), and taipoxin-associated calcium-binding protein 49 (TCBP49). The predominant form of NPR contains an putative NH2-terminal transmembrane domain and all forms of NPR are glycosylated. NPR has 49 and 48% amino acid identity to NP1 and NP2, respectively, and NPR message is expressed in neuronal regions that express NP1 and NP2. We suggest that NPR, NP1, NP2, and TCBP49 are involved in a pathway responsible for the transport of taipoxin into synapses and that this may represent a novel neuronal uptake pathway involved in the clearance of synaptic debris.

Parallel age-associated changes in brain and plasma neuronal pentraxin receptor levels in a transgenic APP/PS1 rat model of Alzheimer's disease

The neuronal pentraxin receptor (NPTXR) as a candidate biomarker of synaptic dysfunction in mild cognitive impairment

Background Alzheimer's disease (AD) is the most prevalent form of dementia. Currently, the most studied biomarkers of AD are cerebrospinal fluid (CSF) amyloid β 1-42, total tau and phosphorylated tau. However, misdiagnosis can exceed 20%. Recently, we found that CSF amyloid β precursor-like protein-1 (APLP1) and neuronal pentraxin receptor (NPTXR) are promising biomarkers of AD. The aim of the present study is to validate CSF APLP1 and NPTXR as biomarkers of AD severity. Methods APLP1 and NPTXR concentrations were measured in the CSF of patients with mild cognitive impairment (MCI) (n = 14), mild AD (n = 21), moderate AD (n = 43) and severe AD (n = 30) using enzyme-linked immunosorbent assays (ELISAs). Results CSF APLP1 and NPTXR were not associated with age or sex. CSF APLP1 was not different between any of the AD severity groups (p = 0.31). CSF NPTXR was significantly different between MCI and mild AD (p = 0.006), mild and moderate AD (p = 0.016), but not between moderate and severe AD (p = 0.36). NPTXR concentration progressively declined from MCI to mild, to moderate and to severe AD patients (p < 0.0001, Kruskal-Wallis test). CSF NPTXR positively correlated with the Mini-Mental Status Examination (MMSE) score (p < 0.001). Conclusions NPTXR concentration in CSF is a promising biomarker of AD severity and could inform treatment success and disease progression in clinical settings.

Neuronal pentraxins modulate cocaine-induced neuroadaptations.

Specific sensitivity of small cell lung cancer cell lines to the snake venom toxin taipoxin

BackgroundControlling metastasis is essential for improving the prognosis of patients with gastric cancer (GC). Here, we aimed to identify a molecule required for GC metastasis and to investigate its potential utility as a target for the development of therapeutic antibodies (Abs).MethodsTranscriptome and bioinformatics analyses of human GC cell lines identified the neuronal pentraxin receptor (NPTXR) as a candidate molecule. NPTXR function was probed by modulating its expression in GC cells and assessing the effects on intracellular signaling and malignant behaviors in vitro and in mouse xenograft models. We also generated anti-NPTXR Abs and Nptxr−/− mice, and assessed the clinical significance of NPTXR expression in GC specimens.ResultsNPTXR mRNA expression in clinical specimens was associated with disease progression and was significantly higher in tissues from GC patients with distant metastasis compared with those without. NPTXR regulated expression of genes involved in metastatic behaviors as well as activation of the PI3K–AKT–mTOR, FAK–JNK, and YAP signaling pathways. NPTXR silencing promoted caspase-mediated apoptosis and attenuated GC cell proliferation, cell cycle progression, migration, invasion, adhesion, stem cell-like properties, and resistance to 5-fluorouracil in vitro, and also inhibited the tumorigenicity of GC cells in vivo. Anti-NPTXR Abs inhibited GC peritoneal metastasis in mice. Nptxr−/− mice showed no abnormalities in reproduction, development, metabolism, or motor function.ConclusionsNPTXR plays an essential role in controlling the malignant behavior of GC cells in vitro and in vivo. NPTXR-targeting Abs may thus have utility as novel diagnostic tools and/or treatment modalities for GC.

Decreased cerebrospinal fluid neuronal pentraxin receptor is associated with PET-Aβ load and cerebrospinal fluid Aβ in a pilot study of Alzheimer’s disease

mGluR1/5-Dependent Long-Term Depression Requires the Regulated Ectodomain Cleavage of Neuronal Pentraxin NPR by TACE

Neuronal pentraxin 1 (NP1), neuronal pentraxin 2 (NP2), and neuronal pentraxin receptor (NPR) are members of a new family of proteins identified through interaction with a presynaptic snake venom toxin taipoxin. We have proposed that these three neuronal pentraxins represent a novel neuronal uptake pathway that may function during synapse formation and remodeling. We have investigated the mutual interactions of these proteins by characterizing their enrichment on taipoxin affinity columns; by expressing NP1, NP2, and NPR singly and together in Chinese hamster ovary cells; and by generating mice that fail to express NP1. NP1 and NP2 are secreted, exist as higher order multimers (probably pentamers), and interact with taipoxin and taipoxin-associated calcium-binding protein 49 (TCBP49). NPR is expressed on the cell membrane and does not bind taipoxin or TCBP49 by itself, but it can form heteropentamers with NP1 and NP2 that can be released from cell membranes. This is the first demonstration of heteromultimerization of pentraxins and release of a pentraxin complex by proteolysis. These processes are likely to directly effect the localization and function of neuronal pentraxins in neuronal uptake or synapse formation and remodeling.

BackgroundAlzheimer's dementia (AD) is a neurodegenerative condition characterized by progressive cognitive decline. Synaptopathy—defined as loss and dysfunction of existing synapses—is a hallmark pathological feature of AD and can directly contribute to underlying cognitive deficits. In this study, we meta‐analyzed several cerebrospinal fluid (CSF) and blood exosomal biomarkers associated with synaptopathy in AD and healthy controls (HCs).MethodOriginal peer‐reviewed articles that reported synaptic biomarker concentrations in CSF or blood exosomes were reviewed. Specifically, synaptosome associated protein‐25 (SNAP‐25), growth associated protein‐43 (GAP‐43), neuronal pentraxin receptor (NPTXR), neuronal pentraxin‐1 (NPTX‐1), neuronal pentraxin‐2 (NPTX‐2), complexin‐2, syntaxin‐1B, syntaxin‐7, and vesicle‐associated membrane protein‐2 (VAMP‐2) in AD and HCs were included for meta‐analysis. A random‐effects model was used to determine standardized mean differences (SMDs) and 95% confidence intervals (CIs). Heterogeneity was quantified using I2.ResultThe meta‐analysis included 43 study cohorts. In CSF, concentrations of SNAP‐25 (NAD/NHC = 394/539, SMD [95% CI] = 1.08 [0.73, 1.42], p < 0.001; I2 = 81.43%), GAP‐43 (NAD/NHC = 851/557, SMD [95% C] = 1.02 [0.69, 1.34], p < 0.001; I2 = 83.97%), and VAMP‐2 (NAD/NHC = 398/490, SMD [95% CI] = 0.32 [0.05, 0.60], p = 0.02; I2 = 64.91%) were elevated, and NPTXR (NAD/NHC = 575/470, SMD [95% CI] = ‐0.68 [‐0.96, ‐0.40], p < 0.001; I2 = 75.59%), NPTX‐1 (NAD/NHC = 344/333, SMD [95% CI] = ‐0.48 [‐0.64, ‐0.31], p < 0.001; I2 = 9.05%), and NPTX‐2 (NAD/NHC = 462/496, SMD [95% CI] = ‐0.78 [‐1.02, ‐0.54], p < 0.001; I2 = 66.43%) were decreased in AD compared to HCs. In blood exosomes, SNAP‐25 (NAD/NHC = 161/159, SMD [95% CI] = ‐1.05 [‐1.28, ‐0.82], p < 0.001; I2 = 0%) and GAP‐43 (NAD/NHC = 110/110, SMD [95% CI] = ‐1.66 [‐2.43, ‐0.88], p < 0.001; I2 = 77%) concentrations were decreased in AD.ConclusionThis study found that several synaptic biomarkers were significantly altered in AD in CSF and blood exosomes. There was significant heterogeneity for most comparisons (with the exception of CSF NPTX‐1 and blood exosome SNAP‐25) that remains to be explored. Nonetheless, further review of the identified biomarkers may provide fundamental insight into AD pathophysiology and disease trajectory.

While previous studies suggest that many mRNAs contain more than one translation initiation site (TIS), the biological significance of most alternative TISs and their corresponding protein isoforms (proteoforms) remains undetermined. Here we show that alternative translation initiation at a CUG and an AUG TIS in neuronal pentraxin receptor (NPR) mRNA produces two proteoforms, and their relative abundance is regulated by both neuronal activity as well as an adjacent RNA secondary structure. Downstream AUG initiation transforms the N-terminal transmembrane domain into a signal peptide, thereby converting NPR to a secreted factor sufficient to promote synaptic clustering of AMPA-type glutamate receptors. Changing the relative proteoform ratio, but not the overall NPR abundance reduces AMPA receptor in parvalbumin (PV)-positive interneurons and induces changes in learning behaviors in mice. In addition to NPR, N-terminal extensions of C1q-like synaptic organizers, mediated by upstream AUU start codons, anchor these otherwise secreted factors to the membrane. Thus, our results uncovered the plasticity of N-terminal signal sequences regulated by alternative TIS usage as a widespread mechanism to diversify protein localization and functions.