成纤维细胞生长因子20(FGF20)-FGF受体1(FGFR1)信号传导对于耳蜗毛细胞(HC)和支持细胞(SC)分化至关重要。在其他器官系统中,FGFR1通过几种细胞内途径发出信号,包括MAPK(ERK),PI3K,磷脂酶C(PLC),p38先前的研究涉及HC和SC发育中的MAPK和PI3K途径。我们假设一个或两个将是HC分化的FGF20-FGFR1信号传导的重要下游介质。
通过抑制耳蜗外植体培养中FGFR1下游的通路,我们确定,MAPK和PI3K途径都是HC分化所必需的,而PLC和p38途径则不是。检查典型的PI3K通路,我们发现,虽然AKT是HC分化所必需的,这不足以挽救Fgf20-/-表型。为了确定PI3K是否在FGF20的下游起作用,我们抑制Fgf20-/-外植体中的磷酸酶和Tensin同源物(PTEN)。PI3K的过度激活导致Fgf20-/-表型的部分挽救,证明了对FGF20下游PI3K的要求。与FGF20调节HC分化的MAPK途径的要求一致,我们表明,用FGF9处理Fgf20-/-外植体增加了dpERK的水平。
一起,这些数据提供了证据,证明MAPK和PI3K都是HC和SC分化过程中FGF20-FGFR1信号传导的重要下游介质.
Fibroblast Growth Factor 20 (FGF20)-FGF receptor 1 (FGFR1) signaling is essential for cochlear hair cell (HC) and supporting cell (SC) differentiation. In other organ systems, FGFR1 signals through several intracellular pathways including MAPK (ERK), PI3K, phospholipase C ɣ (PLCɣ), and p38. Previous studies implicated MAPK and PI3K pathways in HC and SC development. We hypothesized that one or both would be important downstream mediators of FGF20-FGFR1 signaling for HC differentiation.
By inhibiting pathways downstream of FGFR1 in cochlea explant cultures, we established that both MAPK and PI3K pathways are required for HC differentiation while PLCɣ and p38 pathways are not. Examining the canonical PI3K pathway, we found that while AKT is necessary for HC differentiation, it is not sufficient to rescue the Fgf20-/- phenotype. To determine whether PI3K functions downstream of FGF20, we inhibited Phosphatase and Tensin Homolog (PTEN) in Fgf20-/- explants. Overactivation of PI3K resulted in a partial rescue of the Fgf20-/- phenotype, demonstrating a requirement for PI3K downstream of FGF20. Consistent with a requirement for the MAPK pathway for FGF20-regulated HC differentiation, we show that treating Fgf20-/- explants with FGF9 increased levels of dpERK.
Together, these data provide evidence that both MAPK and PI3K are important downstream mediators of FGF20-FGFR1 signaling during HC and SC differentiation.