Limits...
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

The bile salt TUDCA binds the tunnel of ATX.(a,b) The 2mFo-DFc electron density map before ligand placement is contoured at 1.2 RMS and shown as a blue wireframe model in two views; TUDCA (orange carbons; oxygens in red, sulfur in yellow and nitrogen in blue) is shown as a stick model. (c,d) Comparison of the binding of TUDCA and 7α-hydroxycholesterol; Trp260 forms a hydrogen bond (dotted line) with the 3α-OH of TUDCA (in orange), whereas it forms a hydrogen bond with 7α-OH of the hydroxycholesterol (in green). In the TUDCA-bound structure, His251 flips towards the A-ring, whereas in both structures Trp260 and Phe274 pack against the steroid ring system.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4834639&req=5

f4: The bile salt TUDCA binds the tunnel of ATX.(a,b) The 2mFo-DFc electron density map before ligand placement is contoured at 1.2 RMS and shown as a blue wireframe model in two views; TUDCA (orange carbons; oxygens in red, sulfur in yellow and nitrogen in blue) is shown as a stick model. (c,d) Comparison of the binding of TUDCA and 7α-hydroxycholesterol; Trp260 forms a hydrogen bond (dotted line) with the 3α-OH of TUDCA (in orange), whereas it forms a hydrogen bond with 7α-OH of the hydroxycholesterol (in green). In the TUDCA-bound structure, His251 flips towards the A-ring, whereas in both structures Trp260 and Phe274 pack against the steroid ring system.

Mentions: To understand the selectivity of bile salts on ATX activity, we co-crystallized ATX with TUDCA and determined the structure to 2.0 Å resolution (Table 1). Following molecular replacement and model adjustment, there was a clear difference electron density in the tunnel, markedly different from the density for 7HCS (Fig. 4a,b). Owing to the reduction of the C5–C6 double bond of the steroid B-ring, the four-ring system in bile salts is no longer planar, but adopts an L-shaped conformation (Fig. 4b). In comparison with the 7HCS placement, the steroid moiety of TUDCA has ‘slid' inside the tunnel by about 2.5 Å towards the active site (Fig. 4c,d). This movement ‘aligns' the D-ring better with Phe274, likely resulting to more favourable π–π interactions. The Νζ of Trp260 now forms a hydrogen bond with the 3-OH group of the A-ring, instead of the 7-OH that has moved away. In addition, the conserved His251 flips towards the tunnel exit, acting as a ‘lid'. Overall, the ring placement indicates a stronger interaction of TUDCA compared with 7HCS in the tunnel. Given that the tunnel may serve as an LPA exit route9, this observation might provide a mechanism for the inhibitory activity of TUDCA. Unlike the steroid moiety, the acidic tail is not very well resolved in the electron density. Further refinement allowed modelling of three district conformations of the TUDCA acidic tail (Supplementary Fig. 4a,b).


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)

The bile salt TUDCA binds the tunnel of ATX.(a,b) The 2mFo-DFc electron density map before ligand placement is contoured at 1.2 RMS and shown as a blue wireframe model in two views; TUDCA (orange carbons; oxygens in red, sulfur in yellow and nitrogen in blue) is shown as a stick model. (c,d) Comparison of the binding of TUDCA and 7α-hydroxycholesterol; Trp260 forms a hydrogen bond (dotted line) with the 3α-OH of TUDCA (in orange), whereas it forms a hydrogen bond with 7α-OH of the hydroxycholesterol (in green). In the TUDCA-bound structure, His251 flips towards the A-ring, whereas in both structures Trp260 and Phe274 pack against the steroid ring system.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

f4: The bile salt TUDCA binds the tunnel of ATX.(a,b) The 2mFo-DFc electron density map before ligand placement is contoured at 1.2 RMS and shown as a blue wireframe model in two views; TUDCA (orange carbons; oxygens in red, sulfur in yellow and nitrogen in blue) is shown as a stick model. (c,d) Comparison of the binding of TUDCA and 7α-hydroxycholesterol; Trp260 forms a hydrogen bond (dotted line) with the 3α-OH of TUDCA (in orange), whereas it forms a hydrogen bond with 7α-OH of the hydroxycholesterol (in green). In the TUDCA-bound structure, His251 flips towards the A-ring, whereas in both structures Trp260 and Phe274 pack against the steroid ring system.
Mentions: To understand the selectivity of bile salts on ATX activity, we co-crystallized ATX with TUDCA and determined the structure to 2.0 Å resolution (Table 1). Following molecular replacement and model adjustment, there was a clear difference electron density in the tunnel, markedly different from the density for 7HCS (Fig. 4a,b). Owing to the reduction of the C5–C6 double bond of the steroid B-ring, the four-ring system in bile salts is no longer planar, but adopts an L-shaped conformation (Fig. 4b). In comparison with the 7HCS placement, the steroid moiety of TUDCA has ‘slid' inside the tunnel by about 2.5 Å towards the active site (Fig. 4c,d). This movement ‘aligns' the D-ring better with Phe274, likely resulting to more favourable π–π interactions. The Νζ of Trp260 now forms a hydrogen bond with the 3-OH group of the A-ring, instead of the 7-OH that has moved away. In addition, the conserved His251 flips towards the tunnel exit, acting as a ‘lid'. Overall, the ring placement indicates a stronger interaction of TUDCA compared with 7HCS in the tunnel. Given that the tunnel may serve as an LPA exit route9, this observation might provide a mechanism for the inhibitory activity of TUDCA. Unlike the steroid moiety, the acidic tail is not very well resolved in the electron density. Further refinement allowed modelling of three district conformations of the TUDCA acidic tail (Supplementary Fig. 4a,b).

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