A raft-derived, Pak1-regulated entry participates in alpha 2 beta 1 integrin-dependent sorting to caveosomes

作者：Karjalainen Mikko; Kakkonen Elina; Upla Paula; Paloranta Heli; Kankaanpaa Pasi; Liberali Prisca; Renkema G Herma; Hyypia Timo; Heino Jyrki; Marjomaki Varpu^*

来源：Molecular Biology of the Cell, 2008, 19(7): 2857-2869.

DOI：10.1091/mbc.E07-10-1094

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.

• 出版日期2008-7
• 单位河北医科大学