Eisosome

Eisosomes ('eis' meaning into or portal and 'soma', meaning body) are large, heterodimeric, immobile protein complexes at the plasma membrane which mark the site of endocytosis in some eukaryotes, and were discovered in the yeast Saccharomyces cerevisiae in 2006.[1] Currently, seven genes: Pil1, Lsp1 and Sur7,[1] Eis1, Seg1 and Ygr130C,[2] Seg2,[3] are annotated to the formation of the proteins identified in eisosomes.[4] These organelle-like structures have put to rest the idea that sites of endocytosis in cells are chosen at random. Eisosomes have a profound role in regulating plasma membrane architecture and organization in yeast. Microscopic and genetic analyses link these stable, ultrastructural assemblies to the endocytosis of both lipid and protein cargoes in cells.[5]

There are approximately 50–100 eisosomes in each mature yeast cell distributed uniformly across the cell surface periphery in a characteristic dotted pattern[2] with each eisosome containing approximately 2000–5000 copies of Pil1[6] and Lsp1 proteins, as well as, integral membrane protein Sur7.[7] Only a few of the eisosomes present in a cell are active at any one time, suggesting that eisosomes function by using reversible phosphorylation and are regulated portals that govern both location and magnitude of membrane traffic into the cell.

Endocytosis in yeast

The yeast plasma membrane consists of three compartments:

The MCC, a furrow in the plasma membrane, is generated by eisosomes, it disappears in a cell lacking Pil1 which is one of the main eisosome components.[6]

Structural classification

These are large protein complexes composed primarily of subunits of two Bin-Amphiphysin-RVS (BAR) domain containing proteins Pil1 and Lsp1. These two paralogue proteins self-assemble in higher order structure helices and bind preferentially to phosphoinositide-containing membrane. It is also found that eisosome associated proteins Slm1 and Slm 2 have F-BAR domains that are used for targeting furrow like plasma membrane invagination.[5]

References

  1. 1 2 Walther, Tobias C.; Brickner, Jason H.; Aguilar, Pablo S.; Bernales, Sebastián; Pantoja, Carlos; Walter, Peter (2006). "Eisosomes mark static sites of endocytosis". Nature 439 (7079): 998–1003. doi:10.1038/nature04472. PMID 16496001.
  2. 1 2 Deng, C.; Xiong, X.; Krutchinsky, A. N. (2009). "Unifying Fluorescence Microscopy and Mass Spectrometry for Studying Protein Complexes in Cells". Molecular & Cellular Proteomics 8 (6): 1413–23. doi:10.1074/mcp.M800397-MCP200. PMC 2690482. PMID 19269952.
  3. ↑ Seger S and Philippsen P (2010), Personal Communication to SGD
  4. ↑ "Saccharomyces Genome Database".
  5. 1 2 Olivera-Couto, A.; Grana, M.; Harispe, L.; Aguilar, P. S. (2011). "The eisosome core is composed of BAR domain proteins". Molecular Biology of the Cell 22 (13): 2360–72. doi:10.1091/mbc.E10-12-1021. PMC 3128537. PMID 21593205.
  6. 1 2 Moreira, K. E.; Walther, T. C.; Aguilar, P. S.; Walter, P. (2008). "Pil1 Controls Eisosome Biogenesis". Molecular Biology of the Cell 20 (3): 809–18. doi:10.1091/mbc.E08-03-0313. PMC 2633383. PMID 19037108.
  7. ↑ Kamble, Chitra; Jain, Sandhya; Murphy, Erin; Kim, Kyoungtae (2011). "Requirements of Slm proteins for proper eisosome organization, endocytic trafficking and recycling in the yeast Saccharomyces cerevisiae". Journal of Biosciences 36 (1): 79–96. doi:10.1007/s12038-011-9018-0. PMID 21451250.
  8. ↑ Zhang, X; Lester, RL; Dickson, RC (May 21, 2004). "Pil1p and Lsp1p negatively regulate the 3-phosphoinositide-dependent protein kinase-like kinase Pkh1p and downstream signaling pathways Pkc1p and Ypk1p.". The Journal of Biological Chemistry 279 (21): 22030–8. doi:10.1074/jbc.M400299200. PMID 15016821.
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