Hyaluronan regulates transforming growth factor-β1 receptor compartmentalization
Hyaluronan regulates transforming growth factor-β1 receptor compartmentalization
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DOI：
10.1074/jbc.m403135200
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发表时间：
2004-06-11
影响因子：
4.8
通讯作者：
Phillips, AO
中科院分区：
文献类型：
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作者：
Ito, T;Williams, JD;Phillips, AO
转化生长因子-β 1（TGF-β 1）是一种参与许多器官纤维化发病机制的关键细胞因子。我们先前在肾近端小管细胞中证明，细胞外多糖透明质酸与其受体CD 44的结合减弱了TGF-β 1信号传导。在目前的研究中，我们研究了透明质酸（HA）和CD 44之间的相互作用调节TGF-β受体功能的潜在机制。TGF-β受体的亲和标记表明，在未刺激的细胞中，大多数受体分配到EEA-1相关的非脂筏相关的膜池中。在外源性HA的存在下，大多数的受体分配到小窝蛋白-1脂筏相关池。TGF-β 1增加了活化/磷酸化Smad蛋白与EEA-1的结合，这与内体内化后TGF-β 1信号转导的活化一致。加入HA后，小窝蛋白-1与抑制性Smad蛋白Smad 7相关联，与介导受体周转的筏池一致，这是由HA促进的。TGF-β 1依赖性Smad信号传导的拮抗作用和HA对TGF-β受体相关性的作用通过使用制霉菌素消耗膜胆固醇而被抑制，并通过抑制内吞作用而被增强。HA对TGF-β受体运输的作用通过抑制HA-CD 44相互作用、使用CD 44阻断抗体或抑制MAP激酶活化来抑制。总之，我们提出了一个模型，通过该模型，HA参与CD 44导致MAP激酶依赖性增加TGF-β受体向脂筏相关池的转运，这有助于增加受体周转和减弱近端肾小管细胞功能的TGF-β 1依赖性改变。
Transforming growth factor-beta1 (TGF-beta1) is a key cytokine involved in the pathogenesis of fibrosis in many organs. We previously demonstrated in renal proximal tubular cells that the engagement of the extracellular polysaccharide hyaluronan with its receptor CD44 attenuated TGF-beta1 signaling. In the current study we examined the potential mechanism by which the interaction between hyaluronan ( HA) and CD44 regulates TGF-beta receptor function. Affinity labeling of TGF-beta receptors demonstrated that in the unstimulated cells the majority of the receptor partitioned into EEA-1-associated non-lipid raft-associated membrane pools. In the presence of exogenous HA, the majority of the receptors partitioned into caveolin-1 lipid raft-associated pools. TGF-beta1 increased the association of activated/phosphorylated Smad proteins with EEA-1, consistent with activation of TGF-beta1 signaling following endosomal internalization. Following addition of HA, caveolin-1 associated with the inhibitory Smad protein Smad7, consistent with the raft pools mediating receptor turnover, which was facilitated by HA. Antagonism of TGF-beta1-dependent Smad signaling and the effect of HA on TGF-beta receptor associations were inhibited by depletion of membrane cholesterol using nystatin and augmented by inhibition of endocytosis. The effect of HA on TGF-beta receptor trafficking was inhibited by inhibition of HA-CD44 interactions, using blocking antibody to CD44 or inhibition of MAP kinase activation. In conclusion, we have proposed a model by which HA engagement of CD44 leads to MAP kinase-dependent increased trafficking of TGF-beta receptors to lipid raft-associated pools, which facilitates increased receptor turnover and attenuation of TGF-beta1-dependent alteration in proximal tubular cell function.