RESUMO
Store-operated calcium entry (SOCE) is a major pathway for calcium ions influx into cells and has a critical role in various cell functions. Here we demonstrate that calcium-bound calmodulin (Ca2+-CaM) binds to the core region of activated STIM1. This interaction facilitates slow Ca2+-dependent inactivation after Orai1 channel activation by wild-type STIM1 or a constitutively active STIM1 mutant. We define the CaM-binding site in STIM1, which is adjacent to the STIM1-Orai1 coupling region. The binding of Ca2+-CaM to activated STIM1 disrupts the STIM1-Orai1 complex and also disassembles STIM1 oligomer. Based on these results we propose a model for the calcium-bound CaM-regulated deactivation of SOCE.
Assuntos
Cálcio/metabolismo , Calmodulina/metabolismo , Proteínas de Neoplasias/metabolismo , Proteína ORAI1/metabolismo , Molécula 1 de Interação Estromal/metabolismo , Células HEK293 , Humanos , Proteínas de Neoplasias/química , Ligação Proteica , Domínios Proteicos , Molécula 1 de Interação Estromal/químicaRESUMO
Mitochondria Ca2+ overload has long been recognized as a cell death trigger. Unexpectedly, we demonstrated a signaling complex composed of Calmodulin (CaM), Arabidopsis thaliana Bcl-2-associated athanogene 5 (AtBAG5) and Heat-shock cognate 70 protein (Hsc70) within Arabidopsis thaliana mitochondria which transduces mitochondria Ca2+ elevations to suppress leaf senescence. Gain- and loss-of-function AtBAG5 mutant plants revealed that, mitochondria Ca2+ elevation significantly increase chlorophyll retention and decrease H2O2 level in dark-induced leaf senescence assay. Based on our findings, we proposed a molecular mechanism in which chronic mitochondria Ca2+ elevation reduced ROS levels and thus inhibits leaf senescence.
