Small Molecule Investigation of KCNQ Potassium Channels: A Dissertation

Abstract

Voltage-gated K channels associate with multiple regulatory proteins to form complexes with diverse gating properties and pharmacological sensitivities. Small molecules which activate or inhibit channel function are valuable tools for dissecting the assembly and function of these macromolecular complexes. My thesis focuses on the discovery and use of small molecules to probe the structure and function of the KCNQ family of voltage-gated K channels. One protein that obligatorily assembles with KCNQ channels to mediate proper assembly, trafficking, and gating is the calcium sensor, calmodulin. Although resolution of the crystal structures of calmodulin associated with isolated peptide fragments from other ion channels has provided some insight into how calmodulin interacts with and modulates KCNQ channels, structural information for calmodulin bound to a fully folded ion channel in the membrane is unknown. In Chapter II, I developed an intracellular tethered blocker approach to determine the location of calmodulin binding with respect to the KCNQ ion-conducting pathway. Using distance restraints from a panel of these intracellular tethered blockers we then generated models of the KCNQ-calmodulin complex. Our model places calmodulin close to the gate of KCNQ channels, providing structural insight into how CaM is able to communicate changes in intracellular calcium levels to KCNQ channel complexes. In addition to pore blockers, chemical modification of ion channels has been used to probe ion channel function. During my initial attempt to chemically activate KCNQ channels, I discovered that some boronates modulate KCNQ complexes. In Chapter III,