Abstract
Excitotoxic neuronal death induced by high concentrations of glutamate is a pathological event common to multiple acute or chronic neurodegenerative diseases. Excitotoxicity is mediated through overactivation of the N-Methyl-D-aspartate type of ionotropic glutamate receptors (NMDARs). Physiological stimulation of NMDARs triggers their endocytosis from the neuronal surface, inducing synaptic activity and survival. However almost nothing is known about the internalization of overactivated NMDARs and their interacting proteins, and how this endocytic process is connected with neuronal death has been poorly explored. Kinase D-interacting substrate of 220 kDa (Kidins220), also known as ankyrin repeat-rich membrane spanning (ARMS), is a component of NMDAR complexes essential for neuronal viability by the control of ERK activation. Here we have investigated Kidins220 endocytosis induced by NMDAR overstimulation and the participation of this internalization step in the molecular mechanisms of excitotoxicity. We show that excitotoxicity induces Kidins220 and GluN1 traffic to the Golgi apparatus (GA) before Kidins220 is degraded by the protease calpain. We also find that excitotoxicity triggers an early activation of Rap1-GTPase followed by its inactivation. Kidins220 excitotoxic endocytosis and subsequent calpain-mediated downregulation governs this late inactivation of Rap1 that is associated to decreases in ERK activity preceding neuronal death. Furthermore, we identify the molecular mechanisms involved in the excitotoxic shutoff of Kidins220/Rap1/ERK prosurvival cascade that depends on calpain processing of Rap1-activation complexes. Our data fit in a model where Kidins220 targeting to the GA during early excitotoxicity would facilitate Rap1 activation and subsequent stimulation of ERK. At later times, activation of Golgi-associated calpain, would promote the degradation of GA-targeted Kidins220 and two additional components of the specific Rap1 activation complex, PDZ-GEF1, and S-SCAM. In this way, late excitotoxicity would turn off Rap1/ERK cascade and compromise neuronal survival.
Highlights
Overstimulation of the N-Methyl-D-aspartate type of ionotropic glutamate receptors (NMDARs) triggers excitotoxicity, a type of neuronal death that contributes to neurodegeneration in acute neuropathologies and chronic neurodegenerative diseases (Alzheimer’s, Parkinson’s, or Huntington’s)[1]
We show that Kidins[220] excitotoxic endocytosis and subsequent downregulation governs inactivation of the small GTP-ase Rap[1] that controls decreases in extracellular signal-regulated kinase (ERK) activity preceding neuronal death
We identify the molecular mechanisms involved in the excitotoxic shutoff of Kidins220/Rap1/ERKs prosurvival cascade that depends on calpain processing of Rap1-activation complexes
Summary
Overstimulation of the N-Methyl-D-aspartate type of ionotropic glutamate receptors (NMDARs) triggers excitotoxicity, a type of neuronal death that contributes to neurodegeneration in acute neuropathologies (stroke, traumatic brain injury, and epilepsy) and chronic neurodegenerative diseases (Alzheimer’s, Parkinson’s, or Huntington’s)[1]. Activation of NMDARs with physiological concentrations of glutamate is fundamental to neuronal synaptic activity, playing key roles in plasticity, learning and memory[2], as well as neuronal survival. López-Menéndez et al Cell Death and Disease (2019)10:535 through activation of extracellular signal-regulated kinase (ERK)[3]. Function and signaling of NMDARs relie on their spatial and temporal distribution at the neuronal surface where they undergo endocytosis after exposure to nonpathological concentrations of their co-agonists glutamate and glycine[5,6,7,8,9]. Physiological NMDAR internalization is mediated by clathrin/dynamin-dependent endocytosis to Rab5-positive early endosomes[9,10]
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