Bilderback T R, Gazula V R, Dobrowsky R T
Department of Pharmacology and Toxicology, University of Kansas, Lawrence, Kansas, USA.
J Neurochem. 2001 Mar;76(5):1540-51. doi: 10.1046/j.1471-4159.2001.00171.x.
The mechanism of crosstalk between signaling pathways coupled to the Trk A and p75(NTR) neurotrophin receptors in PC12 cells was examined. In response to nerve growth factor (NGF), Trk A activation inhibited p75(NTR)-dependent sphingomyelin (SM) hydrolysis. The phosphoinositide 3-kinase (PI 3-kinase) inhibitor, LY294002, reversed this inhibition suggesting that Trk A activation of PI 3-kinase is necessary to inhibit sphingolipid signaling by p75(NTR). In contrast, SM hydrolysis induced by neurotrophin-3 (NT-3), which did not activate PI-3 kinase, was uneffected by LY294002. However, transient expression of a constituitively active PI 3-kinase inhibited p75(NTR)-dependent SM hydrolysis by both NGF and NT-3. Intriguingly, NGF induced an association of activated PI 3-kinase with acid sphingomyelinase (SMase). This interaction localized to caveolae-related domains and correlated with a 50% decrease in immunoprecipitated acid SMase activity. NGF-stimulated PI 3-kinase activity was necessary for inhibition of acid SMase but was not required for ligand-induced association of the p85 subunit of PI 3-kinase with the phospholipase. Finally, this interaction was specific for NGF since EGF did not induce an association of PI 3-kinase with acid SMase. In summary, our data suggest that PI 3-kinase regulates the inhibitory crosstalk between Trk A tyrosine kinase and p75(NTR)-dependent sphingolipid signaling pathways and that this interaction localizes to caveolae-related domains.
研究了PC12细胞中与Trk A和p75（NTR）神经营养因子受体偶联的信号通路之间的串扰机制。响应神经生长因子（NGF），Trk A激活抑制了p75（NTR）依赖性鞘磷脂（SM）水解。磷酸肌醇3激酶（PI 3激酶）抑制剂LY294002逆转了这种抑制作用，表明PI 3激酶的Trk A激活对于抑制p75（NTR）的鞘脂信号传导是必要的。相比之下，神经营养因子-3（NT-3）诱导的SM水解未激活PI-3激酶，不受LY294002影响。然而，表示组成型活性PI 3激酶的瞬时表达抑制了NGF和NT-3两者的p75（NTR）依赖性SM水解。有趣的是，NGF诱导活化的PI 3激酶与酸性鞘磷脂酶（SMase）缔合。这种相互作用定位于小窝相关结构域，并与免疫沉淀的酸性SMase活性降低50％相关。NGF刺激的PI 3激酶活性是抑制酸性SMase所必需的，但不是PI 3激酶的p85亚基与磷脂酶的配体诱导缔合所必需的。最后，这种相互作用对NGF是特异性的，因为EGF不诱导PI 3激酶与酸性SMase缔合。总之，我们的数据表明PI 3激酶调节Trk A酪氨酸激酶和p75（NTR）依赖性鞘脂信号传导途径之间的抑制性串扰，并且这种相互作用定位于小窝相关结构域。
