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[Localization and expression pattern of MDM2 in axon initial segments of neuron in rodent brain]
Hong Zhao1, Dan-Dan Wang, Yu-Xia Xu
1State Key Laboratory of Medical Neurobiology and Department of Neurobiology, Shanghai Medical College of Fudan University, Shanghai 200032, China. cqzhu@shmu.edu.cn.
Abstract:
To investigate the murine double minute 2 (MDM2) localization and expression pattern in brain, immunohistochemistry, immunofluorescent staining and immunoblotting methods were used to analyze it in brains of Kunming mice during postnatal development, in brains of adult SD rats and in primarily cultured neurons. The distribution of MDM2 and markers of axon initial segment (AIS) was analyzed by double immunolabeling. In addition, Nutlin-3, a MDM2 antagonist, was injected into hippocampus to analyze the effect on the distribution of MDM2 and AIS protein Nav1.6 in AIS. The results showed that the dynamic expression patterns of MDM2 protein in cerebral cortex and hippocampus of Kunming mice after birth were different. However, it was similar that MDM2 was gradually enriched to AIS during postnatal development, especially after postnatal day 7. The MDM2 in AIS was also observed in different brain regions of adult SD rat brain and in primarily cultured neurons, where MDM2 was colocalized with AIS markers such as AnkG and Nav1.6. In addition, hippocampal injection of Nutlin-3 could induce the loss of the characteristic distribution of MDM2 in AIS. Moreover, Nutlin-3 not only caused a decrease of Nav1.6 distributing in AIS, but also disrupted the polarized distribution of MAP2 in neurons. These results indicate that MDM2 can be enriched at the AIS of adult rodent brain, which might play a role in regulation of the maintenance of AIS function and neuronal polarity.
Insights
Murine double minute 2 (MDM2) protein enriches in the axon initial segment (AIS) during rodent brain development. Inhibiting MDM2 disrupts AIS structure and neuronal polarity, suggesting a role in maintaining AIS function.
Area of Science:
- Neuroscience
- Molecular Biology
- Cell Biology
Background:
- The murine double minute 2 (MDM2) protein plays a crucial role in regulating p53 stability.
- Understanding MDM2's function in the central nervous system is essential for neurobiology research.
- The localization and specific roles of MDM2 in neuronal structures remain incompletely understood.
Purpose of the Study:
- To investigate the localization and expression patterns of MDM2 in the rodent brain.
- To determine MDM2's association with the axon initial segment (AIS).
- To elucidate the functional impact of MDM2 modulation on AIS and neuronal polarity.
Main Methods:
- Immunohistochemistry, immunofluorescent staining, and immunoblotting were employed.
- Analysis was performed on Kunming mice during postnatal development and adult SD rats.
- Primary neuronal cultures and in vivo hippocampal injections of Nutlin-3 were utilized.
Main Results:
- MDM2 expression patterns varied dynamically in the developing mouse brain.
- MDM2 progressively accumulated at the AIS during postnatal development, particularly after day 7.
- MDM2 colocalized with AIS markers (AnkG, Nav1.6) in adult rat brains and cultured neurons.
- Nutlin-3 treatment disrupted MDM2 localization at the AIS and reduced Nav1.6 at the AIS.
- Nutlin-3 also impaired the polarized distribution of MAP2 in neurons.
Conclusions:
- MDM2 is enriched at the axon initial segment (AIS) in the adult rodent brain.
- MDM2 accumulation at the AIS may be critical for maintaining AIS function.
- MDM2 appears to play a role in regulating neuronal polarity.
