Benzene Polyphosphates as Tools for Cell Signalling: Inhibition of Inositol 1,4,5‐Trisphosphate 5‐Phosphatase and Interaction with the PH Domain of Protein Kinase Bα

Abstract

Novel benzene polyphosphates were synthesised as inositol polyphosphate mimics and evaluated against type-I inositol 1,4,5-trisphosphate 5-phosphatase, which only binds soluble inositol polyphosphates, and against the PH domain of protein kinase Balpha (PKBalpha), which can bind both soluble inositol polyphosphates and inositol phospholipids. The most potent trisphosphate 5-phosphatase inhibitor is benzene 1,2,4-trisphosphate (2, IC(50) of 14 microM), a potential mimic of D-myo-inositol 1,4,5-trisphosphate, whereas the most potent tetrakisphosphate Ins(1,4,5)P(3) 5-phosphatase inhibitor is benzene 1,2,4,5-tetrakisphosphate, with an IC(50) of 4 microM. Biphenyl 2,3',4,5',6-pentakisphosphate (4) was the most potent inhibitor evaluated against type I Ins(1,4,5)P(3) 5-phosphatase (IC(50) of 1 microM). All new benzene polyphosphates are resistant to dephosphorylation by type I Ins(1,4,5)P(3) 5-phosphatase. Unexpectedly, all benzene polyphosphates studied bind to the PH domain of PKBalpha with apparent higher affinity than to type I Ins(1,4,5)P(3) 5-phosphatase. The most potent ligand for the PKBalpha PH domain, measured by inhibition of biotinylated diC(8)-PtdIns(3,4)P(2) binding, is biphenyl 2,3',4,5',6-pentakisphosphate (4, K(i)=27 nm). The approximately 80-fold enhancement of binding relative to parent benzene trisphosphate is explained by the involvement of a cation-pi interaction. These new molecular tools will be of potential use in structural and cell signalling studies.

ChemInform Abstract: The “Other” Inositols and Their Phosphates: Synthesis, Biology, and Medicine (with Recent Advances in myo‐Inositol Chemistry)

“…[245] Recent data have also focussed upon receptor subtypes in concert with adenophostin analogues. [246] Designing simple synthetic modulators of the Ins(1,4,5)P 3 receptor not based upon inositol that would mimic a myoinositol polyphosphate has always been achallenge.Since the publication of the first antagonist lead, biphenyl 2,3',4,5',6pentakisphosphate BiPh(2,3',4,5',6)P 5 ,( 262;F igure 15), [247] which also exhibits other biological activities, [248] similar compounds have been reported that explore the growing potential of benzene polyphosphates in cell-signaling applications.T hus,anoncarbohydrate/inositol phosphate Ins-(1,4,5)P 3 receptor agonist, based upon ab iphenyl structure and decorated with phosphate groups-biphenyl 3,3',4,4',5,5'hexakisphosphate (BiPh(3,3',4,4',5,5')P 6 , 263)-has been syn-…”

A Synthetic Polyphosphoinositide Headgroup Surrogate in Complex with SHIP2 Provides a Rationale for Drug Discovery

“…To clarify which structural properties of BiPh(2,3′,4,5′,6)P 5 might favor its interaction with SHIP2, we compared its potency with the simpler benzene 1,2,3-trisphosphate (Bz(1,2,3)P 3 ) and benzene 1,2,4,5-tetrakisphosphate (Bz(1,2,4,5)P 4 ) 16 (Figure 1 panel A). Enzyme activity was assayed by measuring inorganic phosphate released from the substrate Ins(1,3,4,5)P 4 (100 μM) using the malachite green phosphate assay (BioAssay Systems).…”

The “Other” Inositols and Their Phosphates: Synthesis, Biology, and Medicine (with Recent Advances inmyo‐Inositol Chemistry)

“…[246] There has always been the challenge to design simple synthetic modulators of the Ins(1,4,5)P 3 receptor not based upon inositol that would mimic a myo-inositol polyphosphate. Since the publication of the first antagonist lead, biphenyl 2,3′,4,5′,6-pentakisphosphate BiPh(2,3′,4,5′,6)P 5 , (262 in Figure 15), [247] which also exhibits other biological activities, [248] …”

“…Designing simple synthetic modulators of the Ins(1,4,5)P 3 receptor not based upon inositol that would mimic a myo ‐inositol polyphosphate has always been a challenge. Since the publication of the first antagonist lead, biphenyl 2,3′,4,5′,6‐pentakisphosphate BiPh(2,3′,4,5′,6)P 5 , ( 262 ; Figure ), which also exhibits other biological activities, similar compounds have been reported that explore the growing potential of benzene polyphosphates in cell‐signaling applications. Thus, a noncarbohydrate/inositol phosphate Ins(1,4,5)P 3 receptor agonist, based upon a biphenyl structure and decorated with phosphate groups—biphenyl 3,3′,4,4′,5,5′‐hexakisphosphate (BiPh(3,3′,4,4′,5,5′)P 6 , 263 )—has been synthesized that surprisingly stimulates the release of Ca 2+ ions .…”