Metabotropic Glutamate Receptor Trafficking and its Role in Drug-Induced Neurobehavioral Plasticity

Metabotropic glutamate receptors-guardians and gatekeepers in neonatal hypoxic-ischemic brain injury

Injury to the developing central nervous system resulting from perinatal hypoxia-ischemia (HI) is still a clinical challenge. The only approach currently available in clinical practice for severe cases of HI is therapeutic hypothermia, initiated shortly after birth and supported by medications to regulate blood pressure, control epileptic seizures, and dialysis to support kidney function. However, these treatments are not effective enough to significantly improve infant survival or prevent brain damage. The need to create a new effective therapy has focused attention on metabotropic glutamate receptors (mGluR), which control signaling pathways involved in HI-induced neurodegeneration. The complexity of mGluR actions, considering their localization and developmental changes, and the functions of each subtype in HI-evoked brain damage, combined with difficulties in the availability of safe and effective modulators, raises the question whether modulation of mGluRs with subtype-selective ligands can become a new treatment in neonatal HI. Addressing this question, this review presents the available information concerning the role of each of the eight receptor subtypes of the three mGluR groups (group I, II, and III). Data obtained from experiments performed on in vitro and in vivo neonatal HI models show the neuroprotective potential of group I mGluR antagonists, as well as group II and III agonists. The information collected in this work indicates that the neuroprotective effects of manipulating mGluR in experimental HI models, despite the need to create more safe and selective ligands for particular receptors, provide a chance to create new therapies for the sensitive brains of infants at risk.

Molecular Mechanisms of AMPA Receptor Trafficking in the Nervous System

Synaptic plasticity enhances or reduces connections between neurons, affecting learning and memory. Postsynaptic AMPARs mediate greater than 90% of the rapid excitatory synaptic transmission in glutamatergic neurons. The number and subunit composition of AMPARs are fundamental to synaptic plasticity and the formation of entire neural networks. Accordingly, the insertion and functionalization of AMPARs at the postsynaptic membrane have become a core issue related to neural circuit formation and information processing in the central nervous system. In this review, we summarize current knowledge regarding the related mechanisms of AMPAR expression and trafficking. The proteins related to AMPAR trafficking are discussed in detail, including vesicle-related proteins, cytoskeletal proteins, synaptic proteins, and protein kinases. Furthermore, significant emphasis was placed on the pivotal role of the actin cytoskeleton, which spans throughout the entire transport process in AMPAR transport, indicating that the actin cytoskeleton may serve as a fundamental basis for AMPAR trafficking. Additionally, we summarize the proteases involved in AMPAR post-translational modifications. Moreover, we provide an overview of AMPAR transport and localization to the postsynaptic membrane. Understanding the assembly, trafficking, and dynamic synaptic expression mechanisms of AMPAR may provide valuable insights into the cognitive decline associated with neurodegenerative diseases.

Glutamate receptor endocytosis and signaling in neurological conditions

The non-essential amino acid glutamate acts as a major excitatory neurotransmitter and plays a significant role in the central nervous system (CNS). It binds with two different types of receptors, ionotropic glutamate receptors (iGluRs) and metabotropic glutamate receptors (mGluRs), responsible for the postsynaptic excitation of neurons. They are important for memory, neural development and communication, and learning. Endocytosis and subcellular trafficking of the receptor are essential for the regulation of receptor expression on the cell membrane and excitation of the cells. The endocytosis and trafficking of the receptor are dependent on its type, ligand, agonist, and antagonist present. This chapter discusses the types of glutamate receptors, their subtypes, and the regulation of their internalization and trafficking. The roles of glutamate receptors in neurological diseases are also briefly discussed.