Abstract
Gap junctions establish direct pathways for cells to transfer metabolic and electrical messages. The local lipid environment is known to affect the structure, stability and intercellular channel activity of gap junctions; however, the molecular basis for these effects remains unknown. Here, we incorporate native connexin-46/50 (Cx46/50) intercellular channels into a dual lipid nanodisc system, mimicking a native cell-to-cell junction. Structural characterization by CryoEM reveals a lipid-induced stabilization to the channel, resulting in a 3D reconstruction at 1.9 Å resolution. Together with all-atom molecular dynamics simulations, it is shown that Cx46/50 in turn imparts long-range stabilization to the dynamic local lipid environment that is specific to the extracellular lipid leaflet. In addition, ~400 water molecules are resolved in the CryoEM map, localized throughout the intercellular permeation pathway and contributing to the channel architecture. These results illustrate how the aqueous-lipid environment is integrated with the architectural stability, structure and function of gap junction communication channels.
Highlights
Gap junctions establish direct pathways for cells to transfer metabolic and electrical messages
The mechanistic principles and biophysical consequences underlying such interactions remains poorly understood, as these interactions are typically lost during protein purification, or remain too dynamic to resolve by traditional structural methods
By exploiting the potential of lipid nanodisc technologies coupled with single-particle CryoEM and molecular dynamics (MD) simulation, we show that Cx46/50 intercellular communication channels form dynamic interactions with annular lipids
Summary
Gap junctions establish direct pathways for cells to transfer metabolic and electrical messages. Tens to 1000s of connexin channels may assemble together to form large hexagonally packed arrays, a.k.a., plaques, known as gap junctions In this way, gap junctions enable the near instantaneous response of electrical synapses in the brain and heart, and contribute to the long-range signaling and metabolic coupling of most tissues. We present an electron cryo-microscopy (CryoEM) structure of native connexin-46/50 (Cx46/50) intercellular channels stabilized in a dual lipid nanodisc system at 1.9 Å resolution —providing a near-atomic level of detail for this class of membrane channels These structural results are coupled with all-atom molecular dynamics (MD) simulation studies, which together reveal many architectural and proposed functional features of the connexin channels. This work uncovers previously unrecognized roles of the aqueous-lipid environment in stabilizing the structure and assembly of the gap junctions, and suggest Cx46/50 plays an important role in shaping the properties of local membrane environment
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