Clathrin adaptor proteins, also known as adaptins, are vesicular transport adaptor proteins associated with clathrin. These proteins are synthesized in the ribosomes, processed in the endoplasmic reticulum and transported from the Golgi apparatus to the trans-Golgi network, and from there via small carrier vesicles to their final destination compartment. The association between adaptins and clathrin are important for vesicular cargo selection and transporting.[1] Clathrin coats contain both clathrin (acts as a scaffold) and adaptor complexes that link clathrin to receptors in coated vesicles. Clathrin-associated protein complexes are believed to interact with the cytoplasmic tails of membrane proteins, leading to their selection and concentration. Therefore, adaptor proteins are responsible for the recruitment of cargo molecules into a growing clathrin-coated pits.[2] The two major types of clathrin adaptor complexes are the heterotetrameric vesicular transport adaptor proteins (AP1-5), and the monomeric GGA (Golgi-localising, Gamma-adaptin ear homology, ARF-binding proteins) adaptors.[3][4] Adaptins are distantly related to the other main type of vesicular transport proteins, the coatomer subunits, sharing between 16% and 26% of their amino acid sequence.[5]
Adaptor protein (AP) complexes are found in coated vesicles and clathrin-coated pits. AP complexes connect cargo proteins and lipids to clathrin at vesicle budding sites, as well as binding accessory proteins that regulate coat assembly and disassembly (such as AP180, epsins and auxilin). There are different AP complexes in mammals. AP1 is responsible for the transport of lysosomal hydrolases between the trans-Golgi network, and endosomes.[6] AP2 adaptor complex associates with the plasma membrane and is responsible for endocytosis.[7] AP3 is responsible for protein trafficking to lysosomes and other related organelles.[8] AP4 is less well characterised. AP complexes are heterotetramers composed of two large subunits (adaptins), a medium subunit (mu) and a small subunit (sigma). For example, in AP1 these subunits are gamma-1-adaptin, beta-1-adaptin, mu-1 and sigma-1, while in AP2 they are alpha-adaptin, beta-2-adaptin, mu-2 and sigma-2. Each subunit has a specific function. Adaptins recognise and bind to clathrin through their hinge region (clathrin box), and recruit accessory proteins that modulate AP function through their C-terminal ear (appendage) domains. Mu recognises tyrosine-based sorting signals within the cytoplasmic domains of transmembrane cargo proteins.[9] One function of clathrin and AP2 complex-mediated endocytosis is to regulate the number of GABAA receptors available at the cell surface .[10]
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Vesicle formation
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See also
References
- ^ McMahon HT, Mills IG (August 2004). "COP and clathrin-coated vesicle budding: different pathways, common approaches". Curr. Opin. Cell Biol. 16 (4): 379–91. doi:10.1016/j.ceb.2004.06.009. PMID 15261670.
- ^ Weigel, Aubrey V.; Tamkun, Michael M.; Krapf, Diego (2013-11-26). "Quantifying the dynamic interactions between a clathrin-coated pit and cargo molecules". Proceedings of the National Academy of Sciences. 110 (48): E4591–E4600. Bibcode:2013PNAS..110E4591W. doi:10.1073/pnas.1315202110. PMC 3845133. PMID 24218552.
- ^ Voglmaier SM, Edwards RH (June 2007). "Do different endocytic pathways make different synaptic vesicles?". Curr. Opin. Neurobiol. 17 (3): 374–80. doi:10.1016/j.conb.2007.04.002. PMID 17449236. S2CID 44740900.
- ^ Boehm M, Bonifacino JS (October 2001). "Adaptins: the final recount". Mol. Biol. Cell. 12 (10): 2907–20. doi:10.1091/mbc.12.10.2907. PMC 60144. PMID 11598180.
- ^ Boehm, Markus; Bonifacino, Juan S. (October 2001). "Adaptins". Molecular Biology of the Cell. 12 (10): 2907–2920. doi:10.1091/mbc.12.10.2907. ISSN 1059-1524. PMC 60144. PMID 11598180.
- ^ Touz MC, Kulakova L, Nash TE (July 2004). "Adaptor protein complex 1 mediates the transport of lysosomal proteins from a Golgi-like organelle to peripheral vacuoles in the primitive eukaryote Giardia lamblia". Mol. Biol. Cell. 15 (7): 3053–60. doi:10.1091/mbc.E03-10-0744. PMC 452563. PMID 15107467.
- ^ Conner SD, Schmid SL (September 2003). "Differential requirements for AP-2 in clathrin-mediated endocytosis". J. Cell Biol. 162 (5): 773–9. doi:10.1083/jcb.200304069. PMC 2172816. PMID 12952931.
- ^ Gupta SN, Kloster MM, Rodionov DG, Bakke O (June 2006). "Re-routing of the invariant chain to the direct sorting pathway by introduction of an AP3-binding motif from LIMP II". Eur. J. Cell Biol. 85 (6): 457–67. doi:10.1016/j.ejcb.2006.02.001. PMID 16542748.
- ^ Haucke V, Wenk MR, Chapman ER, Farsad K, De Camilli P (November 2000). "Dual interaction of synaptotagmin with mu2- and alpha-adaptin facilitates clathrin-coated pit nucleation". EMBO J. 19 (22): 6011–9. doi:10.1093/emboj/19.22.6011. PMC 305843. PMID 11080148.
- ^ Kanematsu T, Fujii M, Mizokami A, Kittler JT, Nabekura J, Moss SJ, Hirata M (May 2007). "Phospholipase C-related inactive protein is implicated in the constitutive internalization of GABAA receptors mediated by clathrin and AP2 adaptor complex". J. Neurochem. 101 (4): 898–905. doi:10.1111/j.1471-4159.2006.04399.x. PMID 17254016. S2CID 22361369.
External links
- Eukaryotic Linear Motif resource motif class TRG_LysEnd_APsAcLL_1
- Eukaryotic Linear Motif resource motif class TRG_LysEnd_APsAcLL_3
This page was last edited on 25 August 2021, at 05:03