During low neuronal activity, increased NP1 expression is evoked, triggering apoptotic neuronal cell death (33) mediated by glycogen synthase kinase-3 (Gsk3) activity (34), and involved in the mitochondrial accumulation of the pro-apoptotic BAX (35)

During low neuronal activity, increased NP1 expression is evoked, triggering apoptotic neuronal cell death (33) mediated by glycogen synthase kinase-3 (Gsk3) activity (34), and involved in the mitochondrial accumulation of the pro-apoptotic BAX (35). immunostaining and co-immunoprecipitation showed that synapse-bound C1q colocalizes and interacts with NPs. High-resolution confocal microscopy revealed that microglia-surrounded C1q-tagged synapses are NP1 positive. We have also observed the synaptic occurrence of C4 suggesting that activation of the classical pathway cannot be ruled out in synaptic plasticity in healthy adult animals. In summary, our results indicate that NPs play a regulatory role in the synaptic function of C1q. Whether this role can be intensified upon pathological conditions, such as in Alzheimers disease, is to be disclosed. forming a large complex with each other and the AMPA-type glutamate receptors, thereby clustering on postsynaptic membranes of excitatory synapses (24, 25). Through their AMPA-receptor binding capabilities, NPs have emerged as potent regulators of excitatory synaptogenesis (26), functional synapse conversion (27), and synaptic plasticity (25, 28). Presynaptic release of NP2 from excitatory axon terminals is neuronal activity-dependent (29C31), and its secretion aids the homeostatic fine-tuning of synaptic transmission in local neuronal networks (32). On the other hand, it has been reported that NP1 acts in neuronal activity-independent manner, and its hetero-oligomers with NP2 exhibit higher clustering activity on AMPA-receptor than NP1 homo-oligomers (25). Apparently 6-TAMRA in contrast to its neuronal activity-independent synaptogenic roles, NP1 also contributes to neuronal cell death and neurodegeneration under adverse conditions in an activation dependent manner. During low neuronal activity, increased NP1 expression is evoked, triggering apoptotic neuronal Rabbit Polyclonal to PITX1 cell death (33) mediated by glycogen synthase kinase-3 (Gsk3) activity (34), and involved in the mitochondrial accumulation of the pro-apoptotic BAX (35). Similarly, NP1 promotes neuronal cell death under hypoxicCischemic conditions (36) and might be an important player in the pathomechanism of neurotoxic amyloid-beta-induced synapse loss, neurite damage, and cell death (37). In sum, NPs are involved in synapse formation and plasticity; moreover, NP1 also serves as a neuronal mediator of harmful external stimuli directing affected neurons to apoptosis. In spite of the huge impact of both the complement and NPs on the synaptic network and their assumed binding capabilities to each other, it remained elusive whether their synaptic functions converge. Therefore, in this study, we systematically examined the potential interaction between C1q and NPs, particularly in the synaptic compartment in adult, wild-type mice. Moreover, we studied whether their interaction plays a role in the microglial phagocytosis of C1q-tagged synapses. Materials and Methods Animals The experiments were conducted on in-house bred 6C8 months old male C57BL/6N mice. Animals were housed under standard laboratory conditions (12:12 h lightCdark cycle with free access to water and food). Antibodies Used in This Study AB1: anti-mouse synaptophysin (#101?006, Synaptic Systems, G?ttingen, Germany); AB2: anti-mouse cytochrome c oxidase subunit 4 (Cox4, #sc-58348, Santa Cruz Biotechnology, Dallas, TX, USA (Santa Cruz)); AB3: anti-mouse actin-(#AC026, Abclonal, Woburn, MA, USA); AB4: anti-mouse 6-TAMRA postsynaptic density protein 95 (Psd95, #MA1-045, Thermo Fisher Scientific (Thermo)); AB5: anti-mouse L-lactate dehydrogenase B (Ldhb, #PAB69Mu01, Cloude-Clone Corp.; Katy, TX, USA), AB6: anti-human and mouse neuronal pentraxin 1 (#20656-1-AP, Proteintech, Rosemont, IL, USA); AB7: anti-human and mouse neuronal pentraxin 2 (#sc-166035, Santa Cruz); AB8: anti-rabbit Alexa Fluor 488-conjugated (#711-545-152, Jackson ImmunoResearch Laboratories, West Grove, PA, USA (Jackson)); AB9: anti-mouse Alexa Fluor 647-conjugated (#715-605-151, Jackson); AB10: anti-human C1qb antibody (#H00000713-D01P, Abnova, Taipei, Taiwan); AB11: anti-mouse secondary antibody, HRP-conjugated (#715-035-150, Jackson), AB12: anti-His-tag antibody (#MA1-21315, Thermo), AB13: anti-human C4BP antibody (#MCA2609, Bio-Rad); AB14: anti-human C4 (A305, Quidel, San Diego, CA, USA); AB15: anti-goat HRP-conjugated (#P0449, Dako, Agilent, Santa Clara, CA, USA); AB16: anti-human neuronal pentraxin 1 (#”type”:”entrez-protein”,”attrs”:”text”:”STJ73037″,”term_id”:”1439351291″,”term_text”:”STJ73037″STJ73037; St Johns Laboratory, London, UK); AB17: anti-human and mouse C1qA (#PAD207Mu01; Cloud-Clone Corp.); AB18: anti-goat Alexa Fluor 488-conjugated (#705-545-147; Jackson); AB19: anti-mouse Alexa Fluor 488-conjugated (#715-545-151, Jackson); AB20: anti-rabbit Alexa Fluor 647-conjugated (1:500 dilution; catalogue number: 715-605-151; Jackson), AB21: anti-mouse C1qA (# “type”:”entrez-nucleotide”,”attrs”:”text”:”AB172451″,”term_id”:”90079666″,”term_text”:”AB172451″AB172451; Abcam, Cambridge, UK); AB22: anti-mouse Iba1 (#234?004, Synaptic Systems); AB23: anti-mouse Alexa Fluor 594-conjugated (#715-585-150, Jackson); AB24: anti-rabbit Cy3-conjugated (#711-165-152; Jackson); AB25: anti-chicken Cy5-conjugated (#703-175-155; Jackson); AB26: anti-guinea pig Alexa Fluor 488-conjugated (#706-545-148; Jackson); AB27: anti-human and mouse neuronal pentraxin 2 (# 10889-1-AP; Proteintech); AB28: anti-mouse synaptophysin (#ab8049; Abcam); AB29: anti-mouse MAP2 (# ab5392; Abcam); AB30: anti-chicken Cy3-conjugated (#703-165-155; Jackson); AB31: rabbit isotype control (#02-6102, Thermo); AB32: mouse isotype control (Mopc, BioLegend); AB33: anti-C4 (#PAA888Mu01, Cloud-Clone Corp.). Dilutions are shown in the descriptions of the corresponding methods. Primary Neuronal Culture Primary neuronal cell culture was prepared from the cerebral cortices 6-TAMRA of mice.