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Protein expression levels of the Src activating protein AFAP are developmentally regulated in brain
David A Clump1, Roger Clem, Yong Qian
1The Mary Babb Randolph Cancer Center and the Department of Microbiology, Immunology and Cell Biology, West Virginia University, Morgantown, West Virginia 26506-9300, USA.
Abstract:
The Src family of nonreceptor tyrosine kinases plays an important role in modulating signals that affect growth cone extension, neuronal differentiation, and brain development. Recent reports indicate that the Src SH2/SH3 binding partner AFAP-110 has the capacity to modulate actin filament integrity as a cSrc activating protein and as an actin filament bundling protein. Both AFAP-110 and a brain specific isoform called AFAP-120 (collectively referred to as AFAP) exist at high levels in chick embryo brain. We sought to identify the localization of AFAP in mouse brain in order to identify its expression pattern and potential role as a cellular modulator of Src family kinase activity and actin filament integrity in the brain. In E16 mouse embryos, AFAP expression levels were very high and concentrated in the olfactory bulb, cortex, forebrain, cerebellum, and various peripheral sensory structures. In P3 mouse pups, overall expression was reduced compared to E16 embryos, and AFAP was found primarily in olfactory bulb, cortex, and cerebellum. AFAP expression levels were significantly reduced in adult mice, with high expression levels only detected in the olfactory bulb. Western blot analysis indicated that concentrated expression of AFAP correlates well with the AFAP-120 isoform, which appears to be a splice variant of AFAP-110. As the expression pattern of AFAP overlaps with the reported expression patterns of cSrc and Fyn, we hypothesize that AFAP is positioned to modulate signal transduction cascades that direct activation of these nonreceptor tyrosine kinases and concomitant cellular changes that occur in actin filaments during brain development.
Insights
AFAP-110 and AFAP-120 (AFAP) are highly expressed in developing mouse brains, particularly in sensory and neuronal regions. Their expression pattern suggests AFAP modulates Src family kinase activity and actin filaments during brain development.
Area of Science:
- Neuroscience
- Cell Biology
- Molecular Biology
Background:
- Src family kinases are crucial for neuronal development, influencing growth cone extension and differentiation.
- AFAP-110, a Src binding partner, modulates actin filament integrity and acts as a Src-activating protein.
- AFAP-110 and its brain-specific isoform AFAP-120 are abundant in chick embryo brains.
Purpose of the Study:
- To determine the localization and expression pattern of AFAP in the developing mouse brain.
- To investigate the potential role of AFAP as a modulator of Src family kinase activity and actin filament integrity.
Main Methods:
- Immunohistochemistry to visualize AFAP expression in E16 embryos, P3 pups, and adult mice.
- Western blot analysis to identify AFAP isoforms and their correlation with expression levels.
Main Results:
- AFAP expression is high in E16 mouse embryos, concentrated in the olfactory bulb, cortex, forebrain, and cerebellum.
- Expression decreases in P3 pups and is significantly reduced in adults, with high levels only in the olfactory bulb.
- Western blots confirm AFAP-120 as a major splice variant correlating with concentrated AFAP expression.
Conclusions:
- AFAP expression patterns in the mouse brain overlap with cSrc and Fyn kinases.
- AFAP is strategically located to modulate Src family kinase signaling pathways.
- AFAP likely plays a role in regulating actin filament dynamics during brain development.