Structure of glutaraldehyde cross-linked ryanodine receptor

Abstract

The ryanodine receptor (RyR) family of calcium release channels plays a vital role in excitation-contraction coupling (ECC). Along with the dihydropyridine receptor (DHPR), calsequestrin, and several other smaller regulatory and adaptor proteins, RyRs form a large dynamic complex referred to as ECC machinery. Here we describe a simple cross-linking procedure that can be used to stabilize fragile components of the ECC machinery, for the purpose of structural elucidation by single particle cryo-electron microscopy (cryo-EM). As a model system, the complex of the FK506-binding protein (FKBP12) and RyR1 was used to test the cross-linking protocol. Glutaraldehyde fixation led to complete cross-linking of receptor-bound FKBP12 to RyR1, and also to extensive cross-linking of the four subunits comprising RyR to one another without compromising the RyR1 ultrastructure. FKBP12 cross-linked with RyR1 was visualized in 2D averages by single particle cryo-EM. Comparison of control RyR1 and cross-linked RyR1 3D reconstructions revealed minor conformational changes at the transmembrane assembly and at the cytoplasmic region. Intersubunit cross-linking enhanced [3H]ryanodine binding to RyR1. Based on our findings we propose that intersubunit cross-linking of RyR1 by glutaraldehyde induced RyR1 to adopt an open like conformation.

Functional Impact of Ryanodine Receptor Oxidation on Intracellular Calcium Regulation in the Heart

“…The protein-protein interaction between RyR2 subunits has been implicated in channel gating (Abramson and Salama 1989; Kimlicka et al 2013; Strauss and Wagenknecht 2013) and, therefore, likely plays an important role in regulating SR Ca 2+ release. In the past decade, there has been a great amount of progress in defining the quaternary structure of RyR (Serysheva et al 2008; Cornea et al 2009; Tung et al 2010; Zalk et al 2015), particularly for the skeletal type 1 isoform (RyR1).…”

“…In these conditions, RyR1 adopted a conformation that resembled that of the open state. In both these studies, the authors suggest that intersubunit cross-linking leads to activation of RyR1 as a result of structural changes that directly affect gating of the channel (Aghdasi et al 1997; Strauss and Wagenknecht 2013). …”