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Steroid binding to Autotaxin links bile salts and lysophosphatidic acid signalling.

Keune WJ, Hausmann J, Bolier R, Tolenaars D, Kremer A, Heidebrecht T, Joosten RP, Sunkara M, Morris AJ, Matas-Rico E, Moolenaar WH, Oude Elferink RP, Perrakis A - Nat Commun (2016)

Bottom Line: Autotaxin (ATX) generates the lipid mediator lysophosphatidic acid (LPA).ATX has a tripartite active site, combining a hydrophilic groove, a hydrophobic lipid-binding pocket and a tunnel of unclear function.Furthermore, our findings suggest potential clinical implications in the use of steroid drugs.

View Article: PubMed Central - PubMed

Affiliation: Division of Biochemistry, Netherlands Cancer Institute, 1066 CX Amsterdam, The Netherlands.

ABSTRACT
Autotaxin (ATX) generates the lipid mediator lysophosphatidic acid (LPA). ATX-LPA signalling is involved in multiple biological and pathophysiological processes, including vasculogenesis, fibrosis, cholestatic pruritus and tumour progression. ATX has a tripartite active site, combining a hydrophilic groove, a hydrophobic lipid-binding pocket and a tunnel of unclear function. We present crystal structures of rat ATX bound to 7α-hydroxycholesterol and the bile salt tauroursodeoxycholate (TUDCA), showing how the tunnel selectively binds steroids. A structure of ATX simultaneously harbouring TUDCA in the tunnel and LPA in the pocket, together with kinetic analysis, reveals that bile salts act as partial non-competitive inhibitors of ATX, thereby attenuating LPA receptor activation. This unexpected interplay between ATX-LPA signalling and select steroids, notably natural bile salts, provides a molecular basis for the emerging association of ATX with disorders associated with increased circulating levels of bile salts. Furthermore, our findings suggest potential clinical implications in the use of steroid drugs.

No MeSH data available.


Related in: MedlinePlus

7α-OH steroids are bound in the tunnel of ATX.(a) A zoom-in to the model with difference density (mFo−DFc) shown as a green wireframe model before any ligand or water placement contoured at 3.5 RMS highlighting the unexplained density in the tunnel. (b) The model is rotated about 90° along the vertical display axis to show the same difference density map. (c) The model is shown in the same orientation as before after including a sterol molecule in the refinement; the resulting 2mFo−DFc map is shown in blue at 1.2 RMS and the difference map in green still indicates a missing atom. (d) The electron density maps after full refinement including the 7α-hydroxycholesterol molecule; all difference density peaks have disappeared. (e) The molecular structure of 7α-hydroxycholesterol showing all atom and ring names.
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f2: 7α-OH steroids are bound in the tunnel of ATX.(a) A zoom-in to the model with difference density (mFo−DFc) shown as a green wireframe model before any ligand or water placement contoured at 3.5 RMS highlighting the unexplained density in the tunnel. (b) The model is rotated about 90° along the vertical display axis to show the same difference density map. (c) The model is shown in the same orientation as before after including a sterol molecule in the refinement; the resulting 2mFo−DFc map is shown in blue at 1.2 RMS and the difference map in green still indicates a missing atom. (d) The electron density maps after full refinement including the 7α-hydroxycholesterol molecule; all difference density peaks have disappeared. (e) The molecular structure of 7α-hydroxycholesterol showing all atom and ring names.

Mentions: During the course of our structural investigation of the ATX catalytic mechanism, we obtained a 1.6-Å resolution structure of ATX (Table 1). Following structure refinement, some residual density in the tunnel became apparent (Fig. 2a,b). The density was compatible with the four-ring system bearing two axially oriented methyl groups, characteristic of steroid moieties. Indeed, modelling of cholesterol in the density yielded a nearly perfect fit (Fig. 2c). To explain remaining difference density, adjacent to the C7 position of the B ring, we modelled 7α-hydroxycholesterol (7HCS, Fig. 2d,e).


Steroid binding to Autotaxin links bile salts and lysophosphatidic acid signalling.

Keune WJ, Hausmann J, Bolier R, Tolenaars D, Kremer A, Heidebrecht T, Joosten RP, Sunkara M, Morris AJ, Matas-Rico E, Moolenaar WH, Oude Elferink RP, Perrakis A - Nat Commun (2016)

7α-OH steroids are bound in the tunnel of ATX.(a) A zoom-in to the model with difference density (mFo−DFc) shown as a green wireframe model before any ligand or water placement contoured at 3.5 RMS highlighting the unexplained density in the tunnel. (b) The model is rotated about 90° along the vertical display axis to show the same difference density map. (c) The model is shown in the same orientation as before after including a sterol molecule in the refinement; the resulting 2mFo−DFc map is shown in blue at 1.2 RMS and the difference map in green still indicates a missing atom. (d) The electron density maps after full refinement including the 7α-hydroxycholesterol molecule; all difference density peaks have disappeared. (e) The molecular structure of 7α-hydroxycholesterol showing all atom and ring names.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4834639&req=5

f2: 7α-OH steroids are bound in the tunnel of ATX.(a) A zoom-in to the model with difference density (mFo−DFc) shown as a green wireframe model before any ligand or water placement contoured at 3.5 RMS highlighting the unexplained density in the tunnel. (b) The model is rotated about 90° along the vertical display axis to show the same difference density map. (c) The model is shown in the same orientation as before after including a sterol molecule in the refinement; the resulting 2mFo−DFc map is shown in blue at 1.2 RMS and the difference map in green still indicates a missing atom. (d) The electron density maps after full refinement including the 7α-hydroxycholesterol molecule; all difference density peaks have disappeared. (e) The molecular structure of 7α-hydroxycholesterol showing all atom and ring names.
Mentions: During the course of our structural investigation of the ATX catalytic mechanism, we obtained a 1.6-Å resolution structure of ATX (Table 1). Following structure refinement, some residual density in the tunnel became apparent (Fig. 2a,b). The density was compatible with the four-ring system bearing two axially oriented methyl groups, characteristic of steroid moieties. Indeed, modelling of cholesterol in the density yielded a nearly perfect fit (Fig. 2c). To explain remaining difference density, adjacent to the C7 position of the B ring, we modelled 7α-hydroxycholesterol (7HCS, Fig. 2d,e).

Bottom Line: Autotaxin (ATX) generates the lipid mediator lysophosphatidic acid (LPA).ATX has a tripartite active site, combining a hydrophilic groove, a hydrophobic lipid-binding pocket and a tunnel of unclear function.Furthermore, our findings suggest potential clinical implications in the use of steroid drugs.

View Article: PubMed Central - PubMed

Affiliation: Division of Biochemistry, Netherlands Cancer Institute, 1066 CX Amsterdam, The Netherlands.

ABSTRACT
Autotaxin (ATX) generates the lipid mediator lysophosphatidic acid (LPA). ATX-LPA signalling is involved in multiple biological and pathophysiological processes, including vasculogenesis, fibrosis, cholestatic pruritus and tumour progression. ATX has a tripartite active site, combining a hydrophilic groove, a hydrophobic lipid-binding pocket and a tunnel of unclear function. We present crystal structures of rat ATX bound to 7α-hydroxycholesterol and the bile salt tauroursodeoxycholate (TUDCA), showing how the tunnel selectively binds steroids. A structure of ATX simultaneously harbouring TUDCA in the tunnel and LPA in the pocket, together with kinetic analysis, reveals that bile salts act as partial non-competitive inhibitors of ATX, thereby attenuating LPA receptor activation. This unexpected interplay between ATX-LPA signalling and select steroids, notably natural bile salts, provides a molecular basis for the emerging association of ATX with disorders associated with increased circulating levels of bile salts. Furthermore, our findings suggest potential clinical implications in the use of steroid drugs.

No MeSH data available.


Related in: MedlinePlus