A raft-derived, Pak1-regulated entry participates in α2β1 integrin-dependent sorting to caveosomes
A raft-derived, Pak1-regulated entry participates in α2β1 integrin-dependent sorting to caveosomes
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DOI：
10.1091/mbc.e07-10-1094
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发表时间：
2008-07-01
影响因子：
3.3
通讯作者：
Marjomaki, Varpu
中科院分区：
文献类型：
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作者：
Karjalainen, Mikko;Kakkonen, Elina;Marjomaki, Varpu
我们之前已经证明，人小核糖核酸病毒埃可病毒1 （EV1）在2小时内与其受体α 2 β 1整合素一起被转运到空泡体。在这里，我们表明大多数早期摄取不是通过小泡发生的。α 2 β 1整合素通过抗体或EV1结合聚集，最初从脂筏内化到管泡结构中。这些囊泡积累了液相标记物，但最初不与小窝蛋白-1或内化的猿猴病毒40 （SV40）共定位。此外，内化的核内体不含糖基磷脂酰肌醇（GPI）锚定蛋白或flotillin 1，这表明聚集性α 2 β 1整合素分别不会进入富含GPI锚定蛋白的核内体腔室或flotillin途径。在15分钟至2小时内，核内体进一步成熟为更大的多泡体，并同时在内部招募小泡蛋白-1或SV40。在saos - α 2 β 1细胞中，细胞进入受p21活化激酶（Pak） 1、Rac1、磷脂酰肌醇3-激酶、磷脂酶C和肌动蛋白的调控，但不受动力蛋白2的调控。阿米洛利类似物5-（n -乙基- n -异丙基）阿米洛利可阻断感染，导致整合素在早期管泡结构中积累，并阻止其结构成熟为多泡结构。我们的研究结果共同表明，α 2 β 1整合素集群定义了自己的进入途径，该途径依赖于Pak1，但不依赖于网格蛋白和小洞蛋白，并且能够将货物分类到小洞体。
We have previously shown that a human picornavirus echovirus 1 (EV1) is transported to caveosomes during 2 h together with its receptor alpha 2 beta 1 integrin. Here, we show that the majority of early uptake does not occur through caveolae. alpha 2 beta 1 integrin, clustered by antibodies or by EV1 binding, is initially internalized from lipid rafts into tubulovesicular structures. These vesicles accumulate fluid-phase markers but do not initially colocalize with caveolin-1 or internalized simian virus 40 (SV40). Furthermore, the internalized endosomes do not contain glycosylphosphatidylinositol (GPI)-anchored proteins or flotillin 1, suggesting that clustered alpha 2 beta 1 integrin does not enter the GPI-anchored protein enriched endosomal compartment or flotillin pathways, respectively. Endosomes mature further into larger multivesicular bodies between 15 min to 2 h and concomitantly recruit caveolin-1 or SV40 inside. Cell entry is regulated by p21-activated kinase (Pak) 1, Rac1, phosphatidylinositol 3-kinase, phospholipase C, and actin but not by dynamin 2 in SAOS-alpha 2 beta 1 cells. An amiloride analog, 5-(N-ethyl-N-isopropanyl) amiloride, blocks infection, causes integrin accumulation in early tubulovesicular structures, and prevents their structural maturation into multivesicular structures. Our results together suggest that alpha 2 beta 1 integrin clustering defines its own entry pathway that is Pak1 dependent but clathrin and caveolin independent and that is able to sort cargo to caveosomes.