| Summary: | 碩士 === 長庚大學 === 基礎醫學研究所 === 92 === Disabled-2 (DAB2) is a structural homolog of Disabled-1, a neuron-specific adaptor protein that participates in positional organization of brain cells during the development. Previous studies have shown that DAB2 is involved in the signal transduction of mitogens, TGFβ, Wnt, and integrin. In addition, DAB2 is implicated as a tumor suppressor that plays a role in the control of proliferation and migration in cancer cells. By western blot analysis of rat brain tissues, we revealed that DAB2 is expressed in various regions of the CNS, with the highest expression level in the olfactory bulb, a unique tissue undergoes repeated episodes of degeneration and regeneration. Although DAB2 has been shown to elicit its function during megakaryocytic differentiation, there is still lack of study to address the role of DAB2 in neuronal tissue. To further address the role of DAB2 in neuronal differentiation, both DAB2 alternative splicing forms, p82 and p59, were stably transfected into pheochromocytoma PC12 cells, respectively. Morphological observations showed that DAB2 significantly reduced nerve growth factor (NGF)-induced PC12 neurite outgrowth. Immunofluorescence data also showed that after NGF stimulation, p59 DAB2 translocated from cytoplasm to plasma membrane, but p82 DAB2 remained in the plasma membrane throughout the treatment, demonstrating the involvement of DAB2 in NGF-induced cell changes. Moreover, by introducing the structural mutations, we found that the DPF motif-contained structure of DAB2 is crucial for its intracellular distribution. Further more, DAB2 overexpression not only blocked the NGF-induced phosphorylation of heat shock protein 27 (HSP27), a microfilament-associated protein, but also increased the hyperphosphorylation levels of tau, a microtubule-associated protein. On the other hand, the neuronal marker, β-tubulin III, was found to associate with DAB2 in coimmunoprecipitation assays, and downregulated during NGF treatment. Together, these findings suggest that DAB2 may play an important role in neuronal differentiation by modulating cytoskeleton stability.
|
|---|
