Structural and Functional Characterization of Phospholipase C β3

Abstract

<b>Abstract ID 24997</b> <b>Poster Board 83</b> Phospholipase C β (PLCβ) plays an important role in cardiovascular diseases and opioid analgesia. PLCβ catalyzes the hydrolysis of the inner membrane lipid into two crucial secondary messengers, phosphatidylinositol-4,5-bisphosphate (PIP₂) to inositol-1,4,5-triphosphate (IP₃) and diacylglycerol (DAG), which activate multiple signaling pathways to modulate cellular behavior. PLCβ is activated downstream of G-protein coupled receptors (GPCRs) by the heterotrimeric G protein subunits Gα_q and Gβγ. In small-angle X-ray scattering (SAXS) experiments, the solution structure of PLCβ had additional density unaccounted for in crystal structures, suggesting that its structure was more dynamic than previously thought. To test this, we used cryo-electron microscopy (cryo-EM) single particle analysis to determine the solution structure of full-length PLCβ3 to 4.1 Å resolution. PLCβ3 adopted a compact, autoinhibited conformation under these conditions. This structure confirmed that the proximal C-terminal domain interacts with the core of PLCβ, but the autoinhibitory X–Y linker does not, suggesting more complex regulation of the lipase by the membrane. We are currently working to determine the structure of PLCβ3 on a model membrane to reveal the basally active state of the lipase.