Dissection of the inhibition of cardiac ryanodine receptors by human glutathione transferase GSTM2-2

Abstract

The muscle specific glutathione transferase GSTM2-2 inhibits the activity of cardiac ryanodine receptor (RyR2) calcium release channels with high affinity and activates skeletal RyR (RyR1) channels with lower affinity. To determine which overall region of the GSTM2-2 molecule supports binding to RyR2, we examined the effects of truncating GSTM2-2 on its ability to alter Ca(2+) release from sarcoplasmic reticulum (SR) vesicles and RyR channel activity. The C-terminal half of GSTM2-2 which lacks the critical GSH binding site supported the inhibition of RyR2, but did not support activation of RyR1. Smaller fragments of GSTM2-2 indicated that the C-terminal helix 6 was crucial for the action of GSTM2-2 on RyR2. Only fragments containing the helix 6 sequence inhibited Ca(2+) release from cardiac SR. Single RyR2 channels were strongly inhibited by constructs containing the helix 6 sequence in combination with adjacent helices (helices 5-8 or 4-6). Fragments containing helices 5-6 or helix 6 sequences alone had less well-defined effects. Chemical cross-linking indicated that C-terminal helices 5-8 bound to RyR2, but not RyR1. Structural analysis with circular dichroism showed that the helical content was greater in the longer helix 6 containing constructs, while the helix 6 sequence alone had minimal helical structure. Therefore the active centre of GSTM2-2 for inhibition of cardiac RyR2 involves the helix 6 sequence and the helical nature of this region is essential for its efficacy. GSTM2-2 helices 5-8 may provide the basis for RyR2-specific compounds for experimental and therapeutic use.

Cardiac Fibroblast-Induced Pluripotent Stem Cell-Derived Exosomes as a Potential Therapeutic Mean for Heart Failure

“…The glutathione transferases (GST) structural family modulates ryanodine receptor (RyR) isolated from muscles (cardiac and skeletal) [ 27 ]. GSTM2 is an inhibitor of cardiac RyR2 [ 28 , 29 ], and it has been shown to be expressed in human skeletal and cardiac muscle [ 30 ]. Hewawasam et al showed that exogenous treatment of neonatal cardiomyocytes with GSTM2 caused a reduction in spontaneous contractility [ 19 ].…”

Glutathione transferases and neurodegenerative diseases

“…In humans GST M2-2 and GST M3-3 but not GST M4-4 have been shown to catalyze the isomerization of prostaglandin (PGH2) to PGE2 (Beuckmann et al, 2000), while the isomerization of PGH2 to PGD2 is catalyzed by Sigma class GSTs (Jowsey et al, 2001). In addition, some GSTs including GST O1-1, GST A1-1, GST M2-2 and chloride intracellular channel proteins (CLIC-2) regulate ryanodine receptor Ca 2+ channels (Board et al, 2004;Dulhunty et al, 2001;Liu et al, 2009). Other GSTs such as GST P1-1 may regulate stress-activated protein kinase (SAPK) signaling pathways by direct binding to JNK (Adler et al, 1999;Elsby et al, 2003) or TNF receptor-associated factor 2 (TRAF2) (Wu et al, 2006).…”

Glutathione Transferases☆

“…Although most of these substances are not the substrates of GSTs, they bind to the GST forms and inhibit their activities. Human GSTM2-2, which is present in the muscle, has been shown to bind to the cardiac muscle ryanodine receptor, thereby inhibiting its activity, which blocks calcium release from the sarcoplasmic reticulum (Liu et al, 2009). The Pi class form possesses cysteine residues that are sensitive to hydrogen peroxide and bind to c-Jun N-terminal kinase (JNK) in order to repress oxidative stress-induced signal transduction (Adler et al, 1999).…”