syntaxin binding protein 1
The STXBP1 gene provides instructions for making syntaxin-binding protein 1. In nerve cells (neurons), this protein helps regulate the release of chemical messengers called neurotransmitters from compartments known as synaptic vesicles. The release of neurotransmitters relays signals between neurons and is critical for normal brain function.
To release its neurotransmitters, a synaptic vesicle must join (fuse) with the outer membrane of the neuron. The syntaxin-binding protein 1 regulates the formation of a group (complex) of proteins that allows vesicle fusion.
At least 85 mutations in the STXBP1 gene have been found to cause STXBP1 encephalopathy with epilepsy. This condition is characterized by recurrent seizures (epilepsy) that begin in infancy, abnormal brain function (encephalopathy), and intellectual disability. The mutations can alter the structure of the syntaxin-binding protein 1, result in an abnormally short protein, or add or delete small sections of the protein.
The gene mutations that cause STXBP1 encephalopathy with epilepsy reduce the amount of functional syntaxin-binding protein 1 produced from the gene. A shortage of this protein impairs the formation of the protein complex that allows vesicle fusion and the release of neurotransmitters from neurons. A change in neurotransmitter levels can lead to uncontrolled activation (excitation) of neurons, which causes seizures. This altered neuronal activity does not appear to impair the development or survival of neurons; the cause of the encephalopathy and other neurological problems in this condition is unclear.
At least three mutations in the STXBP1 gene have been found to cause a condition called ataxia-tremor-retardation syndrome. This condition is characterized by difficulty coordinating movements (ataxia), involuntary trembling (tremors), intellectual disability, and developmental delay. Unlike, STXBP1 encephalopathy with epilepsy (described above), individuals with ataxia-tremor-retardation syndrome do not develop seizures. It is unclear why STXBP1 gene mutations cause seizures in some individuals and not in others.
- neuronal SEC1