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EEA1, or early endosome antigen 1, is a membrane bound Rab5 effector protein specific to the early endosome and plays an important role in membrane trafficking. Early endosomes fuse with endocytic vesicles to redistribute compounds to other cellular destinations. EEA1 contains a C-terminal FYVE domain that binds to phosphatidylinositol-3-phosphate, which targets it to early endosomes [1, 2]. EEA1 is essential for early endosome docking together with SNARES contained on endocytic vesicles, allowing for membrane fusion .
Co-staining with antibodies against organelle markers can confirm localization of a protein of interest to a specific cellular compartment. For example, immunohistochemistry using an antibody against EEA1 showed mCherry vesicles colocalized with EEA1, indicating that the mCherry vesicles were involved in the early endocytic pathway . Further, EEA1 is often used simply as a marker protein for early endosomal vesicles in experiments involving cell fractionation. To be sure a cytosolic fraction is pure, it is important to check for contamination of endosomal vesicles, which may be achieved by western blotting of the EEA1 protein, which is exclusive to early endosomes . If extracted cells contain EEA1 (detected by the EEA1 antibody), while the cytosolic fraction does not, this fraction is known to be free of early endosome contamination.
Interestingly, intracellular pathogens may interfere with normal intracellular trafficking mechanisms, including that of EEA1. To give one example, researchers demonstrated using an EEA1 antibody that Listeria monocytogenes colocalizes with EEA1 during entry . Further, the Listeria residing in an EEA1 enriched vacuole may favor vacuolar fusion with early endosomes, delaying phagosomal maturation .
Novus Biologicals offers EEA1 reagents for your research needs including:
1. Stenmark, H., et al., Endosomal localization of the autoantigen EEA1 is mediated by a zinc-binding FYVE finger. J Biol Chem, 1996. 271(39): p. 24048-54.
2. Patki, V., et al., Identification of an early endosomal protein regulated by phosphatidylinositol 3-kinase. Proc Natl Acad Sci U S A, 1997. 94(14): p. 7326-30.
3. Christoforidis, S., et al., The Rab5 effector EEA1 is a core component of endosome docking. Nature, 1999. 397(6720): p. 621-5.
4. Chen, Y.T., et al., R26R-GR: a Cre-activable dual fluorescent protein reporter mouse. PLoS One, 2012. 7(9): p. e46171.
5. Fahrer, J., J. Rausch, and H. Barth, A Cell-Permeable Fusion Protein Based on Clostridium botulinumC2 Toxin for Delivery of p53 Tumorsuppressor into Cancer Cells. PLoS ONE, 2013. 8(9): p. e72455.
6. Veiga, E. and P. Cossart, Listeria hijacks the clathrin-dependent endocytic machinery to invade mammalian cells. Nat Cell Biol, 2005. 7(9): p. 894-900.
7. Pizarro-Cerda, J. and P. Cossart, Subversion of phosphoinositide metabolism by intracellular bacterial pathogens. Nat Cell Biol, 2004. 6(11): p. 1026-1033.