Autotaxin, also known as ectonucleotide pyrophosphatase/phosphodiesterase family member 2 (E-NPP 2), is an enzyme that in humans is encoded by the ENPP2gene.[1][2]
Autotaxin was originally identified as a tumor cell-motility-stimulating factor; later it was shown to be LPA (which signals through lysophospholipid receptors), the lipid product of the reaction catalyzed by autotaxin, which is responsible for its effects on cell-proliferation.
The protein encoded by this gene functions as a phosphodiesterase. Autotaxin is secreted and further processed to make the biologically active form. Several alternatively spliced transcript variants have been identified. Autotaxin is able to cleave the phosphodiester bond between the α and the β position of triphosphate nucleotides, acting as an ectonucleotide phosphodiesterase producing pyrophosphate, as most members of the ENPP family. Importantly, autotaxin also acts as phospholipase, catalyzing the removal of the head group of various lysolipids. The physiological function of autotaxin is the production of the signalling lipid lysophosphatidic acid (LPA) in extracellular fluids. LPA evokes growth factor-like responses including stimulation of cell proliferation and chemotaxis. This gene product stimulates the motility of tumor cells, has angiogenic properties, and its expression is up-regulated in several kinds of tumours.[2] Also, autotaxin and LPA are involved in numerous inflammatory-driven diseases such as asthma and arthritis.[3] Physiologically, LPA helps promote wound healing responses to tissue damage. Under normal circumstances, LPA negatively regulates autotaxin transcription, but in the context of wound repair, cytokines induce autotaxin expression to increase overall LPA concentrations.[4]
It has been shown that autotaxin's function can be regulated by certain steroids, namely bile acids.[5]
As a drug target
Various small molecule inhibitors of autotaxin have been developed for clinical applications. A specific inhibitor against idiopathic pulmonary fibrosis showed promising results in a phase II trial that ended in May 2018.[6] A DNA aptamer inhibitor of Autotaxin has also been described.[7]
Structure
The crystal structures rat[8] and mouse autotaxin[9] have been solved. In each case, the apo structure have been solved along with product or inhibitor bound complexes. Both proteins consist of 4 domains, 2 N-terminal somatomedin-B-like (SMB) domains which may be involved in cell-surface localisation. The catalytic domain follows and contains a deep hydrophobic pocket in which the lipid substrate binds. At the C-terminus is the inactive nuclease domain which may function to aid protein stability.
↑Kawagoe H, Soma O, Goji J, Nishimura N, Narita M, Inazawa J, Nakamura H, Sano K (November 1995). "Molecular cloning and chromosomal assignment of the human brain-type phosphodiesterase I/nucleotide pyrophosphatase gene (PDNP2)". Genomics. 30 (2): 380–4. doi:10.1006/geno.1995.0036. PMID8586446.
↑Benesch MG, Ko YM, McMullen TP, Brindley DN (August 2014). "Autotaxin in the crosshairs: taking aim at cancer and other inflammatory conditions". FEBS Letters. 588 (16): 2712–27. doi:10.1016/j.febslet.2014.02.009. PMID24560789.
↑Clinical trial number NCT02738801 for "Study to Assess Safety, Tolerability, Pharmacokinetic and Pharmacodynamic Properties of GLPG1690" at ClinicalTrials.gov
↑Kato K, Ikeda H, Miyakawa S, Futakawa S, Nonaka Y, Fujiwara M, Okudaira S, Kano K, Aoki J, Morita J, Ishitani R, Nishimasu H, Nakamura Y, Nureki O (May 2016). "Structural basis for specific inhibition of Autotaxin by a DNA aptamer". Nature Structural & Molecular Biology. 23 (5): 395–401. doi:10.1038/nsmb.3200. PMID27043297.
Tokumura A, Majima E, Kariya Y, Tominaga K, Kogure K, Yasuda K, Fukuzawa K (October 2002). "Identification of human plasma lysophospholipase D, a lysophosphatidic acid-producing enzyme, as autotaxin, a multifunctional phosphodiesterase". The Journal of Biological Chemistry. 277 (42): 39436–42. doi:10.1074/jbc.M205623200. PMID12176993.
Stracke ML, Krutzsch HC, Unsworth EJ, Arestad A, Cioce V, Schiffmann E, Liotta LA (February 1992). "Identification, purification, and partial sequence analysis of autotaxin, a novel motility-stimulating protein". The Journal of Biological Chemistry. 267 (4): 2524–9. PMID1733949.
Stracke ML, Arestad A, Levine M, Krutzsch HC, Liotta LA (August 1995). "Autotaxin is an N-linked glycoprotein but the sugar moieties are not needed for its stimulation of cellular motility". Melanoma Research. 5 (4): 203–9. doi:10.1097/00008390-199508000-00001. PMID7496154.
Murata J, Lee HY, Clair T, Krutzsch HC, Arestad AA, Sobel ME, Liotta LA, Stracke ML (December 1994). "cDNA cloning of the human tumor motility-stimulating protein, autotaxin, reveals a homology with phosphodiesterases". The Journal of Biological Chemistry. 269 (48): 30479–84. PMID7982964.
Lee HY, Murata J, Clair T, Polymeropoulos MH, Torres R, Manrow RE, Liotta LA, Stracke ML (January 1996). "Cloning, chromosomal localization, and tissue expression of autotaxin from human teratocarcinoma cells". Biochemical and Biophysical Research Communications. 218 (3): 714–9. doi:10.1006/bbrc.1996.0127. PMID8579579.
Lee HY, Clair T, Mulvaney PT, Woodhouse EC, Aznavoorian S, Liotta LA, Stracke ML (October 1996). "Stimulation of tumor cell motility linked to phosphodiesterase catalytic site of autotaxin". The Journal of Biological Chemistry. 271 (40): 24408–12. doi:10.1074/jbc.271.40.24408. PMID8798697.
Clair T, Lee HY, Liotta LA, Stracke ML (January 1997). "Autotaxin is an exoenzyme possessing 5'-nucleotide phosphodiesterase/ATP pyrophosphatase and ATPase activities". The Journal of Biological Chemistry. 272 (2): 996–1001. doi:10.1074/jbc.272.2.996. PMID8995394.
Dias Neto E, Correa RG, Verjovski-Almeida S, Briones MR, Nagai MA, da Silva W, Zago MA, Bordin S, Costa FF, Goldman GH, Carvalho AF, Matsukuma A, Baia GS, Simpson DH, Brunstein A, de Oliveira PS, Bucher P, Jongeneel CV, O'Hare MJ, Soares F, Brentani RR, Reis LF, de Souza SJ, Simpson AJ (March 2000). "Shotgun sequencing of the human transcriptome with ORF expressed sequence tags". Proceedings of the National Academy of Sciences of the United States of America. 97 (7): 3491–6. doi:10.1073/pnas.97.7.3491. PMC16267. PMID10737800.
Nam SW, Clair T, Kim YS, McMarlin A, Schiffmann E, Liotta LA, Stracke ML (September 2001). "Autotaxin (NPP-2), a metastasis-enhancing motogen, is an angiogenic factor". Cancer Research. 61 (18): 6938–44. PMID11559573.
Tokumura A, Majima E, Kariya Y, Tominaga K, Kogure K, Yasuda K, Fukuzawa K (October 2002). "Identification of human plasma lysophospholipase D, a lysophosphatidic acid-producing enzyme, as autotaxin, a multifunctional phosphodiesterase". The Journal of Biological Chemistry. 277 (42): 39436–42. doi:10.1074/jbc.M205623200. PMID12176993.
Jung ID, Lee J, Yun SY, Park CG, Choi WS, Lee HW, Choi OH, Han JW, Lee HY (December 2002). "Cdc42 and Rac1 are necessary for autotaxin-induced tumor cell motility in A2058 melanoma cells". FEBS Letters. 532 (3): 351–6. doi:10.1016/S0014-5793(02)03698-0. PMID12482591.
Yang SY, Lee J, Park CG, Kim S, Hong S, Chung HC, Min SK, Han JW, Lee HW, Lee HY (2003). "Expression of autotaxin (NPP-2) is closely linked to invasiveness of breast cancer cells". Clinical & Experimental Metastasis. 19 (7): 603–8. doi:10.1023/A:1020950420196. PMID12498389.
Gijsbers R, Aoki J, Arai H, Bollen M (March 2003). "The hydrolysis of lysophospholipids and nucleotides by autotaxin (NPP2) involves a single catalytic site". FEBS Letters. 538 (1–3): 60–4. doi:10.1016/S0014-5793(03)00133-9. PMID12633853.
Koh E, Clair T, Woodhouse EC, Schiffmann E, Liotta L, Stracke M (May 2003). "Site-directed mutations in the tumor-associated cytokine, autotaxin, eliminate nucleotide phosphodiesterase, lysophospholipase D, and motogenic activities". Cancer Research. 63 (9): 2042–5. PMID12727817.
Kehlen A, Englert N, Seifert A, Klonisch T, Dralle H, Langner J, Hoang-Vu C (May 2004). "Expression, regulation and function of autotaxin in thyroid carcinomas". International Journal of Cancer. 109 (6): 833–8. doi:10.1002/ijc.20022. PMID15027116.
van Meeteren LA, Ruurs P, Christodoulou E, Goding JW, Takakusa H, Kikuchi K, Perrakis A, Nagano T, Moolenaar WH (June 2005). "Inhibition of autotaxin by lysophosphatidic acid and sphingosine 1-phosphate". The Journal of Biological Chemistry. 280 (22): 21155–61. doi:10.1074/jbc.M413183200. PMID15769751.