LGIC gene family

Genes in the LGIC gene family provide instructions for making ligand-gated ion channels. These channels span the membrane that surrounds cells and form a hole (pore) through which positively or negatively charged atoms (ions), such as sodium, potassium, calcium, or chloride ions, can flow. The flow of ions is triggered by the attachment (binding) of proteins called ligands. Each channel is "opened" by the binding of a particular ligand. The ligands that open ligand-gated ion channels are called neurotransmitters because they transmit signals in the brain.

Genes in the LGIC family can be divided into several groups based on the ligand that binds to the channel. Nicotinic acetylcholine receptors are triggered by the binding of a chemical called acetylcholine. Serotonin type 3 (5-HT₃) receptors are triggered by serotonin. GABA_A receptors are triggered by gamma-aminobutyric acid (GABA). Ionotropic glutamate receptors are triggered by glutamate. Glycine receptors are triggered by glycine. Ionotropic purinergic receptors are triggered by a chemical called adenosine triphosphate (ATP). And zinc-activated channels are triggered by zinc.

Ligand-gated ion channels play an important role in the nervous system. The channels are primarily found in nerve cells (neurons) in the brain, spinal cord, and muscles, and they function to control the transmission of nerve impulses from neuron to neuron or neuron to muscle. The flow of positively charged ions into the cell turns on (excites) nerve impulses. In contrast, the flow of negatively charged ions into the cell blocks (inhibits) nerve impulses to prevent the nervous system from being overloaded with too many signals. Nicotinic acetylcholine receptors, 5-HT₃ receptors, and ionotropic glutamate receptors allow the flow of positively charged sodium, potassium, and, sometimes, calcium ions, which excites nerve signaling. Similarly, ionotropic purinergic receptors allow calcium ions to cross the cell membrane, exciting nerve signaling. GABA_A and glycine receptors allow the flow of negatively charged chloride ions, and so these channels inhibit nerve signaling. The function of zinc channels is unknown.

Signaling in the brain through ligand-gated ion channels is important for many neurological functions, including learning, memory formation, movement of muscles, and reflexes. Mutations in genes in the LGIC family can lead to neurological disorders such as seizures, movement difficulties, and abnormal muscle stiffness and weakness.