3h85

Structural highlights

Disease

[PI51C_HUMAN] Defects in PIP5K1C are the cause of lethal congenital contracture syndrome type 3 (LCCS3) [MIM:611369]; also known as multiple contractural syndrome Israeli Bedouin type B. LCCS is an autosomal recessive disorder characterized by early fetal hydrops and akinesia, the Pena-Shokeir phenotype, specific neuropathology with degeneration of anterior horn neurons and extreme skeletal muscle atrophy. LCCS3 patients present at birth with severe multiple joint contractures with severe muscle wasting and atrophy, mainly in the legs. LCCS3 can be distinguished from the original LCCS by the absence of hydrops, fractures, and multiple pterygia.^[1]

Function

[AP2M1_RAT] Component of the adaptor protein complex 2 (AP-2). Adaptor protein complexes function in protein transport via transport vesicles in different membrane traffic pathways. Adaptor protein complexes are vesicle coat components and appear to be involved in cargo selection and vesicle formation. AP-2 is involved in clathrin-dependent endocytosis in which cargo proteins are incorporated into vesicles surrounded by clathrin (clathrin-coated vesicles, CCVs) which are destined for fusion with the early endosome. The clathrin lattice serves as a mechanical scaffold but is itself unable to bind directly to membrane components. Clathrin-associated adaptor protein (AP) complexes which can bind directly to both the clathrin lattice and to the lipid and protein components of membranes are considered to be the major clathrin adaptors contributing the CCV formation. AP-2 also serves as a cargo receptor to selectively sort the membrane proteins involved in receptor-mediated endocytosis. AP-2 seems to play a role in the recycling of synaptic vesicle membranes from the presynaptic surface. AP-2 recognizes Y-X-X-[FILMV] (Y-X-X-Phi) and [ED]-X-X-X-L-[LI] endocytosis signal motifs within the cytosolic tails of transmembrane cargo molecules. AP-2 may also play a role in maintaining normal post-endocytic trafficking through the ARF6-regulated, non-clathrin pathway. The AP-2 mu subunit binds to transmembrane cargo proteins; it recognizes the Y-X-X-Phi motifs. The surface region interacting with to the Y-X-X-Phi motif is inaccessible in cytosolic AP-2, but becomes accessible through a conformational change following phosphorylation of AP-2 mu subunit at 'Tyr-156' in membrane-associated AP-2. The membrane-specific phosphorylation event appears to involve assembled clathrin which activates the AP-2 mu kinase AAK1 (By similarity). Plays a role in endocytosis of frizzled family members upon Wnt signaling.^{[2] [3] [4] [5]} [PI51C_HUMAN] Catalyzes the phosphorylation of phosphatidylinositol 4-phosphate (PtdIns4P) to form phosphatidylinositol 4,5-bisphosphate (PtdIns(4,5)P2). PtdIns(4,5)P2 is involved in a variety of cellular processes and is the substrate to form phosphatidylinositol 3,4,5-trisphosphate (PtdIns(3,4,5)P3), another second messenger. The majority of PtdIns(4,5)P2 is thought to occur via type I phosphatidylinositol 4-phosphate 5-kinases given the abundance of PtdIns4P. Participates in a variety of cellular processes such as vesicle mediated transport, cell adhesion, cell polarization and cell migration. Together with PIP5K1A is required for phagocytosis, but they regulate different types of actin remodeling at sequential steps. Promotes particle attachment by generating the pool of PtdIns(4,5)P2 that induces controlled actin depolymerization to facilitate Fc-gamma-R clustering. Mediates RAC1-dependent reorganization of actin filaments. Required for synaptic vesicle transport. Controls the plasma membrane pool of PtdIns(4,5)P2 implicated in synaptic vesicle endocytosis and exocytosis. Plays a role in endocytosis mediated by clathrin and AP-2 (adaptor protein complex 2). Required for clathrin-coated pits assembly at the synapse. Participates in cell junction assembly. Modulates adherens junctions formation by facilitating CDH1 trafficking. Required for focal adhesion dynamics. Modulates the targeting of talins (TLN1 and TLN2) to the plasma membrane and their efficient assembly into focal adhesions. Regulates the interaction between talins (TLN1 and TLN2) and beta-integrins. Required for uropodium formation and retraction of the cell rear during directed migration. Has a role in growth factor- stimulated directional cell migration and adhesion. Required for talin assembly into nascent adhesions forming at the leading edge toward the direction of the growth factor. Negative regulator of T-cell activation and adhesion. Negatively regulates integrin alpha-L/beta-2 (LFA-1) polarization and adhesion induced by T-cell receptor. Together with PIP5K1A have a role during embryogenesis and together with PIP5K1B may have a role immediately after birth.^{[6] [7] [8] [9]}

Evolutionary Conservation

Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf.

See Also

• Adaptin 3D structures

References

1. ↑ Narkis G, Ofir R, Landau D, Manor E, Volokita M, Hershkowitz R, Elbedour K, Birk OS. Lethal contractural syndrome type 3 (LCCS3) is caused by a mutation in PIP5K1C, which encodes PIPKI gamma of the phophatidylinsitol pathway. Am J Hum Genet. 2007 Sep;81(3):530-9. Epub 2007 Jul 24. PMID:17701898 doi:S0002-9297(07)61349-4
2. ↑ Olusanya O, Andrews PD, Swedlow JR, Smythe E. Phosphorylation of threonine 156 of the mu2 subunit of the AP2 complex is essential for endocytosis in vitro and in vivo. Curr Biol. 2001 Jun 5;11(11):896-900. PMID:11516654
3. ↑ Nakatsu F, Ohno H. Adaptor protein complexes as the key regulators of protein sorting in the post-Golgi network. Cell Struct Funct. 2003 Oct;28(5):419-29. PMID:14745134
4. ↑ Owen DJ, Collins BM, Evans PR. Adaptors for clathrin coats: structure and function. Annu Rev Cell Dev Biol. 2004;20:153-91. PMID:15473838 doi:10.1146/annurev.cellbio.20.010403.104543
5. ↑ Yu A, Xing Y, Harrison SC, Kirchhausen T. Structural analysis of the interaction between Dishevelled2 and clathrin AP-2 adaptor, a critical step in noncanonical Wnt signaling. Structure. 2010 Oct 13;18(10):1311-20. PMID:20947020 doi:10.1016/j.str.2010.07.010
6. ↑ Di Paolo G, Pellegrini L, Letinic K, Cestra G, Zoncu R, Voronov S, Chang S, Guo J, Wenk MR, De Camilli P. Recruitment and regulation of phosphatidylinositol phosphate kinase type 1 gamma by the FERM domain of talin. Nature. 2002 Nov 7;420(6911):85-9. PMID:12422219 doi:10.1038/nature01147
7. ↑ Krauss M, Kinuta M, Wenk MR, De Camilli P, Takei K, Haucke V. ARF6 stimulates clathrin/AP-2 recruitment to synaptic membranes by activating phosphatidylinositol phosphate kinase type Igamma. J Cell Biol. 2003 Jul 7;162(1):113-24. PMID:12847086 doi:10.1083/jcb.200301006
8. ↑ Ling K, Bairstow SF, Carbonara C, Turbin DA, Huntsman DG, Anderson RA. Type I gamma phosphatidylinositol phosphate kinase modulates adherens junction and E-cadherin trafficking via a direct interaction with mu 1B adaptin. J Cell Biol. 2007 Jan 29;176(3):343-53. PMID:17261850 doi:10.1083/jcb.200606023
9. ↑ Sun Y, Ling K, Wagoner MP, Anderson RA. Type I gamma phosphatidylinositol phosphate kinase is required for EGF-stimulated directional cell migration. J Cell Biol. 2007 Jul 16;178(2):297-308. PMID:17635937 doi:10.1083/jcb.200701078
10. ↑ Kahlfeldt N, Vahedi-Faridi A, Koo SJ, Schafer JG, Krainer G, Keller S, Saenger W, Krauss M, Haucke V. Molecular basis for association of PIPKI gamma-p90 with clathrin adaptor AP-2. J Biol Chem. 2010 Jan 22;285(4):2734-49. Epub 2009 Nov 10. PMID:19903820 doi:10.1074/jbc.M109.074906