TY - JOUR
T1 - Junctin – the quiet achiever
AU - Dulhunty, Angela F.
AU - Wei, Lan
AU - BEARD, Nicole
PY - 2009
Y1 - 2009
N2 - Recent advances in understanding skeletal and cardiac muscle function have evolved with recognition of the active role played by the intracellular sarcoplasmic reticulum (SR) Ca2+ store in contraction. The key proteins in this store are the Ca2+ binding protein calsequestrin (CSQ), the ryanodine receptor (RyR) Ca2+ release channel and triadin and junctin (Beard et al. 2004). The CSQ–triadin–junctin–RyR complex (Fig. 1) in the SR lumen forms a ‘Ca2+ transduction machine’ that is central to EC coupling and to normal muscle development. Other proteins in the lumen of the SR, including the histidine rich calcium binding protein (HRC) (Suk et al. 1999), JP‐45 (Anderson et al. 2003) and SRP‐27 (Bleunven et al. 2008), must also contribute to control of SR intraluminal Ca2+ load, but the precise nature of their role remains undetermined. JP‐45 in particular is ideally placed to communicate store load to the excitation–contraction (EC) coupling process as it binds to both CSQ and the dihydropyridine receptor (DHPR) in the surface/transverse tubule membrane. The importance of the luminal proteins has been underlined by the recent discovery that changes in Ca2+ signalling due to mutations in CSQ or to lack of its expression can result in sudden cardiac death (Viatchenko‐Karpinski et al. 2004). Furthermore, studies in animal models show that changes in CSQ, junctin, triadin and HRC expression can lead to defective Ca2+ signalling. The review by Pritchard & Kranius (2009) examines the roles of junctin and HRC in Ca2+ cycling and their potential significance in heart failure. This commentary focuses on protein‐protein interactions between CSQ, triadin, junctin and RyR proteins that may underlie their roles in Ca2+ cycling.
AB - Recent advances in understanding skeletal and cardiac muscle function have evolved with recognition of the active role played by the intracellular sarcoplasmic reticulum (SR) Ca2+ store in contraction. The key proteins in this store are the Ca2+ binding protein calsequestrin (CSQ), the ryanodine receptor (RyR) Ca2+ release channel and triadin and junctin (Beard et al. 2004). The CSQ–triadin–junctin–RyR complex (Fig. 1) in the SR lumen forms a ‘Ca2+ transduction machine’ that is central to EC coupling and to normal muscle development. Other proteins in the lumen of the SR, including the histidine rich calcium binding protein (HRC) (Suk et al. 1999), JP‐45 (Anderson et al. 2003) and SRP‐27 (Bleunven et al. 2008), must also contribute to control of SR intraluminal Ca2+ load, but the precise nature of their role remains undetermined. JP‐45 in particular is ideally placed to communicate store load to the excitation–contraction (EC) coupling process as it binds to both CSQ and the dihydropyridine receptor (DHPR) in the surface/transverse tubule membrane. The importance of the luminal proteins has been underlined by the recent discovery that changes in Ca2+ signalling due to mutations in CSQ or to lack of its expression can result in sudden cardiac death (Viatchenko‐Karpinski et al. 2004). Furthermore, studies in animal models show that changes in CSQ, junctin, triadin and HRC expression can lead to defective Ca2+ signalling. The review by Pritchard & Kranius (2009) examines the roles of junctin and HRC in Ca2+ cycling and their potential significance in heart failure. This commentary focuses on protein‐protein interactions between CSQ, triadin, junctin and RyR proteins that may underlie their roles in Ca2+ cycling.
KW - junctin
KW - sarcoplasmic-reticulum-calcium-signalling
KW - muscle-contraction
U2 - 10.1113/jphysiol.2009.171959
DO - 10.1113/jphysiol.2009.171959
M3 - Article
SN - 1469-7793
VL - 587
SP - 3135
EP - 3137
JO - The Journal of Physiology
JF - The Journal of Physiology
IS - 13
ER -