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Neurite-promoting effect of alpha 2-macroglobulin in rat cerebral cortex is mainly associated with alpha
1Department of Biological Sciences, Faculty of Bioscience and Biotechnology, Tokyo Institute of Technology, Yokohama, Japan.
Abstract:
It has been reported that alpha 2-macroglobulin (alpha 2 M), known as a plasma protease inhibitor, promotes neurite outgrowth of cultured neurons from rat cerebral cortex. The neurons dissociated from 17-day embryonic (E17) rat cerebral cortex were cultured in the medium containing methylamine-modified alpha 2M labeled with fluorescein isothiocyanate (MA- alpha 2 M-FITC). The modified alpha 2 M was taken up by neurons and localized mainly at the base of neurites. The fluorescence intensity of internalized MA- alpha 2 M-FITC in the cell was correlated to the degree of neurites extension. An immunocytochemical study using anti-alpha 2 M receptor (alpha 2 MR) polyclonal antibody showed that the neurons cultured for a longer period were stained weaker than those cultured for a shorter period. Many alpha 2 MRs were expressed when the neurons were likely to be extending the neurites well. From the developmental study of rat cerebrum, the expression of alpha 2 MR reached a maximum at postnatal 2 days (P2) when the neurons started to exhibit active neurite extension. These observations led us to conclude that neurite promoting effect of alpha 2 M acts through alpha 2 M-alpha 2MR binding and/or the following uptake of alpha 2 M.
Insights
Alpha 2-macroglobulin (alpha 2 M), a plasma protease inhibitor, promotes neurite outgrowth in cultured rat neurons. This effect is mediated by alpha 2 M binding to its receptor (alpha 2 MR) and subsequent cellular uptake.
Area of Science:
- Neuroscience
- Biochemistry
- Cell Biology
Background:
- Alpha 2-macroglobulin (alpha 2 M) is a known plasma protease inhibitor.
- Previous studies suggest alpha 2 M may influence neuronal development.
Purpose of the Study:
- To investigate the role of alpha 2 M in promoting neurite outgrowth in cultured rat cortical neurons.
- To elucidate the mechanism by which alpha 2 M exerts its neurite-promoting effects.
Main Methods:
- Culturing embryonic rat cortical neurons with methylamine-modified alpha 2M labeled with fluorescein isothiocyanate (MA-alpha 2M-FITC).
- Utilizing immunocytochemistry with anti-alpha 2 M receptor (alpha 2 MR) polyclonal antibody.
- Conducting a developmental study of alpha 2 MR expression in the rat cerebrum.
Main Results:
- MA-alpha 2M-FITC was internalized by neurons and localized at neurite bases, with fluorescence intensity correlating to neurite extension.
- Neurons cultured longer showed weaker staining for alpha 2 MR, while higher alpha 2 MR expression correlated with active neurite extension.
- Alpha 2 MR expression peaked at postnatal day 2 (P2), coinciding with active neurite extension in rat cerebrum.
Conclusions:
- Alpha 2 M promotes neurite outgrowth in cultured cortical neurons.
- The neurite-promoting effect of alpha 2 M is likely mediated through binding to its receptor (alpha 2 MR) and subsequent cellular uptake.