Scott K Adney

Virginia Commonwealth University, Richmond, VA, United States

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Publications (10)62.29 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: Anionic phospholipids are critical constituents of the inner leaflet of the plasma membrane, ensuring appropriate membrane topology of transmembrane proteins. Additionally, in eukaryotes, the negatively charged phosphoinositides serve as key signals not only through their hydrolysis products but also through direct control of transmembrane protein function. Direct phosphoinositide control of the activity of ion channels and transporters has been the most convincing case of the critical importance of phospholipidprotein interactions in the functional control of membrane proteins. Furthermore, second messengers, such as [Ca(2+)]i, or posttranslational modifications, such as phosphorylation, can directly or allosterically fine-tune phospholipid-protein interactions and modulate activity. Recent advances in structure determination of membrane proteins have allowed investigators to obtain complexes of ion channels with phosphoinositides and to use computational and experimental approaches to probe the dynamic mechanisms by which lipid-protein interactions control active and inactive protein states. Expected final online publication date for the Annual Review of Physiology Volume 77 is February 10, 2015. Please see http://www.annualreviews.org/catalog/pubdates.aspx for revised estimates.
    Annual review of physiology. 10/2014;
  • Biophysical Journal 01/2013; 104(2):24-. · 3.67 Impact Factor
  • Biophysical Journal 01/2013; 104(2):130-. · 3.67 Impact Factor
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    ABSTRACT: Kir channels play an important role in setting the resting membrane potential and modulating membrane excitability. An emerging feature of several Kir channels is that they are regulated by cholesterol. Yet, the mechanism by which cholesterol affects channel function is unclear. Here we show that mutations of two distant Kir2.1 cytosolic residues, L222 and N251, form a two-way molecular switch that controls channel modulation by cholesterol, and affects critical hydrogen bonding. Notably, these two residues are linked by a residue-chain that continues from N251 to connect adjacent subunits. Furthermore, our data indicate that the same switch also regulates the sensitivity of the channels to PI(4,5)P(2), a phosphoinositide which is required for activation of Kir channels. Thus, although cholesterol and PI(4,5)P(2) do not interact with the same region of Kir2.1, these different modulators induce a common gating pathway of the channel.
    Journal of Biological Chemistry 09/2012; · 4.65 Impact Factor
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    ABSTRACT: Voltage-gated K(+) (Kv) channels couple the movement of a voltage sensor to the channel gate(s) via a helical intracellular region, the S4-S5 linker. A number of studies link voltage sensitivity to interactions of S4 charges with membrane phospholipids in the outer leaflet of the bilayer. Although the phospholipid phosphatidylinositol-4,5-bisphosphate (PIP(2)) in the inner membrane leaflet has emerged as a universal activator of ion channels, no such role has been established for mammalian Kv channels. Here we show that PIP(2) depletion induced two kinetically distinct effects on Kv channels: an increase in voltage sensitivity and a concomitant decrease in current amplitude. These effects are reversible, exhibiting distinct molecular determinants and sensitivities to PIP(2). Gating current measurements revealed that PIP(2) constrains the movement of the sensor through interactions with the S4-S5 linker. Thus, PIP(2) controls both the movement of the voltage sensor and the stability of the open pore through interactions with the linker that connects them.
    Proceedings of the National Academy of Sciences 08/2012; 109(36):E2399-408. · 9.81 Impact Factor
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    ABSTRACT: Over the past 16 years, there has been an impressive number of ion channels shown to be sensitive to the major phosphoinositide in the plasma membrane, phosphatidylinositol 4,5-bisphosphate (PIP(2)). Among them are voltage-gated channels, which are crucial for both neuronal and cardiac excitability. Voltage-gated calcium (Cav) channels were shown to be regulated bidirectionally by PIP(2). On one hand, PIP(2) stabilized their activity by reducing current rundown but on the other hand it produced a voltage-dependent inhibition by shifting the activation curve to more positive voltages. For voltage-gated potassium (Kv) channels PIP(2) was first shown to prevent N-type inactivation regardless of whether the fast inactivation gate was part of the pore-forming α subunit or of an accessory β subunit. Careful examination of the effects of PIP(2) on the activation mechanism of Kv1.2 has shown a similar bidirectional regulation as in the Cav channels. The two effects could be distinguished kinetically, in terms of their sensitivities to PIP(2) and by distinct molecular determinants. The rightward shift of the Kv1.2 voltage dependence implicated basic residues in the S4-S5 linker and was consistent with stabilization of the inactive state of the voltage sensor. A third type of a voltage-gated ion channel modulated by PIP(2) is the hyperpolarization-activated cyclic nucleotide-gated (HCN) channel. PIP(2) has been shown to enhance the opening of HCN channels by shifting their voltage-dependent activation toward depolarized potentials. The sea urchin HCN channel, SpIH, showed again a PIP(2)-mediated bidirectional effect but in reverse order than the depolarization-activated Cav and Kv channels: a voltage-dependent potentiation, like the mammalian HCN channels, but also an inhibition of the cGMP-induced current activation. Just like the Kv1.2 channels, distinct molecular determinants underlied the PIP(2) dual effects on SpIH, with the proximal C-terminus implicated in the inhibitory effect. The dual regulation of these very different ion channels, all of which are voltage-dependent, points to conserved mechanisms of regulation of these channels by PIP(2).
    Frontiers in Pharmacology 01/2012; 3:170.
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    ABSTRACT: Atypical antipsychotic drugs, such as clozapine and risperidone, have a high affinity for the serotonin 5-HT(2A) G protein-coupled receptor (GPCR), the 2AR, which signals via a G(q) heterotrimeric G protein. The closely related non-antipsychotic drugs, such as ritanserin and methysergide, also block 2AR function, but they lack comparable neuropsychological effects. Why some but not all 2AR inhibitors exhibit antipsychotic properties remains unresolved. We now show that a heteromeric complex between the 2AR and the G(i)-linked GPCR, metabotropic glutamate 2 receptor (mGluR2), integrates ligand input, modulating signaling output and behavioral changes. Serotonergic and glutamatergic drugs bind the mGluR2/2AR heterocomplex, which then balances Gi- and Gq-dependent signaling. We find that the mGluR2/2AR-mediated changes in Gi and Gq activity predict the psychoactive behavioral effects of a variety of pharmocological compounds. These observations provide mechanistic insight into antipsychotic action that may advance therapeutic strategies for disorders including schizophrenia and dementia.
    Cell 11/2011; 147(5):1011-23. · 31.96 Impact Factor
  • Biophysical Journal - BIOPHYS J. 01/2011; 100(3).
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    ABSTRACT: The plasma membrane phosphoinositide phosphatidylinositol 4,5-bisphosphate (PIP2) controls the activity of most ion channels tested thus far through direct electrostatic interactions. Mutations in channel proteins that change their apparent affinity to PIP2 can lead to channelopathies. Given the fundamental role that membrane phosphoinositides play in regulating channel activity, it is surprising that only a small number of channelopathies have been linked to phosphoinositides. This review proposes that for channels whose activity is PIP2-dependent and for which mutations can lead to channelopathies, the possibility that the mutations alter channel-PIP2 interactions ought to be tested. Similarly, diseases that are linked to disorders of the phosphoinositide pathway result in altered PIP2 levels. In such cases, it is proposed that the possibility for a concomitant dysregulation of channel activity also ought to be tested. The ever-growing list of ion channels whose activity depends on interactions with PIP2 promises to provide a mechanism by which defects on either the channel protein or the phosphoinositide levels can lead to disease.
    Pflügers Archiv - European Journal of Physiology 07/2010; 460(2):321-41. · 4.87 Impact Factor
  • Biophysical Journal 01/2009; 96(3). · 3.67 Impact Factor

Publication Stats

121 Citations
62.29 Total Impact Points

Institutions

  • 2011–2012
    • Virginia Commonwealth University
      • • Department of Physiology and Biophysics
      • • School of Medicine
      Richmond, VA, United States
    • Mount Sinai School of Medicine
      • Department of Structural and Chemical Biology
      Manhattan, NY, United States