1m5n

Structural highlights

Disease

[PTHR_HUMAN] Defects in PTHLH are the cause of brachydactyly type E2 (BDE2) [MIM:613382]. BDE2 is a form of brachydactyly. Brachydactyly defines a group of inherited malformations characterized by shortening of the digits due to abnormal development of the phalanges and/or the metacarpals. Brachydactyly type E is characterized by shortening of the fingers mainly in the metacarpals and metatarsals. Wide variability in the number of digits affected occurs from person to person, even in the same family. Some individuals are moderately short of stature. In brachydactyly type E2 variable combinations of metacarpals are involved, with shortening also of the first and third distal and the second and fifth middle phalanges.^[1]

Function

[IMB1_HUMAN] Functions in nuclear protein import, either in association with an adapter protein, like an importin-alpha subunit, which binds to nuclear localization signals (NLS) in cargo substrates, or by acting as autonomous nuclear transport receptor. Acting autonomously, serves itself as NLS receptor. Docking of the importin/substrate complex to the nuclear pore complex (NPC) is mediated by KPNB1 through binding to nucleoporin FxFG repeats and the complex is subsequently translocated through the pore by an energy requiring, Ran-dependent mechanism. At the nucleoplasmic side of the NPC, Ran binds to importin-beta and the three components separate and importin-alpha and -beta are re-exported from the nucleus to the cytoplasm where GTP hydrolysis releases Ran from importin. The directionality of nuclear import is thought to be conferred by an asymmetric distribution of the GTP- and GDP-bound forms of Ran between the cytoplasm and nucleus. Mediates autonomously the nuclear import of ribosomal proteins RPL23A, RPS7 and RPL5. Binds to a beta-like import receptor binding (BIB) domain of RPL23A. In association with IPO7 mediates the nuclear import of H1 histone. In vitro, mediates nuclear import of H2A, H2B, H3 and H4 histones. In case of HIV-1 infection, binds and mediates the nuclear import of HIV-1 Rev. Imports PRKCI into the nucleus.^{[2] [3] [4]} [PTHR_HUMAN] Neuroendocrine peptide which is a critical regulator of cellular and organ growth, development, migration, differentiation and survival and of epithelial calcium ion transport. Regulates endochondral bone development and epithelial-mesenchymal interactions during the formation of the mammary glands and teeth. Required for skeletal homeostasis. Promotes mammary mesenchyme differentiation and bud outgrowth by modulating mesenchymal cell responsiveness to BMPs. Upregulates BMPR1A expression in the mammary mesenchyme and this increases the sensitivity of these cells to BMPs and allows them to respond to BMP4 in a paracrine and/or autocrine fashion. BMP4 signaling in the mesenchyme, in turn, triggers epithelial outgrowth and augments MSX2 expression, which causes the mammary mesenchyme to inhibit hair follicle formation within the nipple sheath (By similarity). Promotes colon cancer cell migration and invasion in an integrin alpha-6/beta-1-dependent manner through activation of Rac1.^[5] Osteostatin is a potent inhibitor of osteoclastic bone resorption.^[6]

Evolutionary Conservation

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

See Also

• Importin 3D structures

References

1. ↑ Klopocki E, Hennig BP, Dathe K, Koll R, de Ravel T, Baten E, Blom E, Gillerot Y, Weigel JF, Kruger G, Hiort O, Seemann P, Mundlos S. Deletion and point mutations of PTHLH cause brachydactyly type E. Am J Hum Genet. 2010 Mar 12;86(3):434-9. doi: 10.1016/j.ajhg.2010.01.023. Epub, 2010 Feb 18. PMID:20170896 doi:10.1016/j.ajhg.2010.01.023
2. ↑ Jakel S, Gorlich D. Importin beta, transportin, RanBP5 and RanBP7 mediate nuclear import of ribosomal proteins in mammalian cells. EMBO J. 1998 Aug 3;17(15):4491-502. PMID:9687515 doi:10.1093/emboj/17.15.4491
3. ↑ Jakel S, Albig W, Kutay U, Bischoff FR, Schwamborn K, Doenecke D, Gorlich D. The importin beta/importin 7 heterodimer is a functional nuclear import receptor for histone H1. EMBO J. 1999 May 4;18(9):2411-23. PMID:10228156 doi:10.1093/emboj/18.9.2411
4. ↑ White WO, Seibenhener ML, Wooten MW. Phosphorylation of tyrosine 256 facilitates nuclear import of atypical protein kinase C. J Cell Biochem. 2002;85(1):42-53. PMID:11891849
5. ↑ Mula RV, Bhatia V, Falzon M. PTHrP promotes colon cancer cell migration and invasion in an integrin alpha6beta4-dependent manner through activation of Rac1. Cancer Lett. 2010 Dec 1;298(1):119-27. doi: 10.1016/j.canlet.2010.06.009. Epub, 2010 Jul 15. PMID:20637541 doi:10.1016/j.canlet.2010.06.009
6. ↑ Mula RV, Bhatia V, Falzon M. PTHrP promotes colon cancer cell migration and invasion in an integrin alpha6beta4-dependent manner through activation of Rac1. Cancer Lett. 2010 Dec 1;298(1):119-27. doi: 10.1016/j.canlet.2010.06.009. Epub, 2010 Jul 15. PMID:20637541 doi:10.1016/j.canlet.2010.06.009
7. ↑ Cingolani G, Bednenko J, Gillespie MT, Gerace L. Molecular basis for the recognition of a nonclassical nuclear localization signal by importin beta. Mol Cell. 2002 Dec;10(6):1345-53. PMID:12504010