The nuclear localization of CAPON in hippocampus and cerebral cortex neurons after lipopolysaccharide stimulation.
OBJECTIVE
In the brain, nitric oxide (NO) is a retrograde signalling molecule that transfers information from post- to pre-synaptic nerve endings. NO has been shown to be an important inflammatory mediator responding to lipopolysaccharide (LPS). It has been stated that the constitutive NO synthase isoforms (nNOS and eNOS) may also contribute to the inflammation. CAPON, a nNOS regulator, helps regulate nNOS stability, localization and possibly expression during synapse formation as well as muscle re-innervation. Recently, it has been reported that CAPON is associated with psychiatric illness. So we speculated that the CAPON expression-induced physiological changes may be mediated by modifications of NOS-NO signalling pathways. But little is known about the role of CAPON during the inflammation in the central nervous system, so we investigated the expression of CAPON in the brain treated with LPS.


RESULTS
Real-time PCR and Western blot showed that the expression of CAPON increased at mRNA and protein levels in the brain after LPS stimulation. Immunocytochemistry staining revealed that CAPON localized in the nuclei of neurons in the brain after peritoneal injection with LPS in vivo. The same phenomenon was also shown in primary cultured neurons in vitro incubated with LPS for 36 h. In addition, we found that CAPON had a colocalization with phosphorylated nNOS Ser847 but not with nNOS in hippocampus and cerebral cortex by double immunofluorescence.


CONCLUSIONS
CAPON localized in the nuclei of neurons in hippocampus and cerebral cortex after LPS treatment. Because CAPON competed with PSD-95 for binding nNOS in neurons and nNOS was activated to produce NO through the NMDA- NMDAR pathway, we hypothesized that CAPON might play a proactive role in the process of inflammation by transferring from cytoplasm to the nucleus and through the NMDA-nNOS signal pathway. Further studies are required to clarify the mechanism of the nuclear localization of CAPON and the possible relationship with nNOS/NO signalling.
Department of Neurosurgery, Affiliated Dongtai Hospital of Nantong University, Jiangsu Key Laboratory of Neuroregeneration, Nantong University, Nantong, PR China.
Bai
B
Shao
Jing
J
Jiang
Qiyun
Q
Wu
Yanyan
Y
Xu
Qingshan
Q
Lv
Xiaohong
X
Li
Ping
P
Wang
Aiguo
A
Shen
Meijuan
M
Yan
D048868:Adaptor Proteins, Signal Transducing / Q000378:metabolism*; D000818:Animals; D015153:Blotting, Western; D002467:Cell Nucleus / Q000187:drug effects / Q000378:metabolism*; D002540:Cerebral Cortex / Q000378:metabolism*; D005455:Fluorescent Antibody Technique; D006624:Hippocampus / Q000187:drug effects / Q000378:metabolism*; D007150:Immunohistochemistry; D007249:Inflammation / Q000139:chemically induced / Q000378:metabolism; D008070:Lipopolysaccharides / Q000494:pharmacology; D008297:Male; D009474:Neurons / Q000378:metabolism*; D052248:Nitric Oxide Synthase Type I / Q000378:metabolism; D021381:Protein Transport / Q000502:physiology; D051381:Rats; D017208:Rats, Wistar; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000502:physiology
D048868:Adaptor Proteins, Signal Transducing; D008070:Lipopolysaccharides; C488082:NOS1AP protein, rat; D052248:Nitric Oxide Synthase Type I