Premium
Potent inhibition of phosphodiesterase‐5 (PDE5) by vardenafil, but not by sildenafil, tadalafil, or IBMX requires an intact GAF b domain
Author(s) -
Blount Mitsi A,
Zoraghi Roya,
Corbin Jackie D,
Francis Sharron H
Publication year - 2006
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.20.4.a543-c
Subject(s) - vardenafil , tadalafil , ibmx , cgmp specific phosphodiesterase type 5 , sildenafil , chemistry , pharmacology , phosphodiesterase , medicine , biochemistry , enzyme , receptor , forskolin
PDE5 contains a catalytic domain that hydrolyzes cGMP and a regulatory domain that includes two GAFs ( a and b ). Cyclic GMP allosteric binding to GAF a increases catalytic site affinity for cGMP and inhibitors, but GAF b influence has not been demonstrated. Amino‐terminal truncations of PDE5 that include a complete GAF b (PDE5 ΔT322‐N875 and PDE5ΔE430‐N875), lack a complete GAF b (PDE5 ΔG466‐N875), or have no GAF b sequence (PDE5 ΔE535‐Q860) had substrate K m values that were equivalent to that of wild type PDE5Δ(PDE5 WT ). IC 50 values for IBMX, sildenafil, tadalafil, and UK 122764, were equivalent to one another and to PDE5 WT . However, potencies of PDE5 WT , PDE5 ΔT322‐N875, and PDE5 ΔE430‐N875 yielded IC 50 s for vardenafil that were ~9‐fold lower than PDE5 ΔG466‐N875 and PDE5 ΔE535‐Q860. These results were repeated using demethyl‐vardenafil and the vardenafil based compound, BAY 51–1871. Binding isotherm experiments with [ 3 H]vardenafil reveal that PDE5 WT has a ~7‐fold higher affinity for vardenafil than does PDE5 ΔE535‐Q860. Data demonstrate that GAF b contributes to potent PDE5 inhibition by vardenafil and other vardenafil based compounds, but not for cGMP, sildenafil, tadalafil, UK 122764, or IBMX. These findings are the first to establish the importance of GAF b for selective enhancement of PDE5 catalytic site affinity for an inhibitor. DK58277