Local changes in GTP-binding protein immunoreactivities in human epileptogenic neocortex

Area of Science:

• Neuroscience
• Molecular Biology
• Biochemistry

Background:

• Epilepsy is a neurological disorder characterized by recurrent seizures.
• Guanine nucleotide-binding proteins (G proteins) are crucial signal transducers in neuronal function.
• Alterations in G protein expression may contribute to the pathophysiology of epilepsy.

Purpose of the Study:

• To investigate the relative levels of specific G protein alpha-subunits in the neocortex of patients with intractable temporal lobe epilepsy.
• To compare G protein expression in actively spiking versus non-spiking cortical regions.
• To determine if G protein levels correlate with seizure susceptibility.

Main Methods:

• Neocortical tissue samples were obtained from epilepsy surgery patients.
• Specific polyclonal antisera were used to quantify G protein alpha-subunits (Gi1α, Gi2α, Gi3α, Go(α), Gs(α), Gx/z(α)) via Laurell "rocket" immunoelectrophoresis.
• Intraoperative electrocorticography (ECoG) identified spiking (active) and non-spiking (non-active) cortical regions.

Main Results:

• No consistent differences in G protein subtype levels were found between spiking and non-spiking regions across all patients.
• Paired analysis within individual patients revealed significant increases or decreases in certain G protein subtypes in spiking versus non-spiking cortex.
• These findings suggest microzonal alterations in G protein levels associated with neuronal activity.

Conclusions:

• Neuronal activity in epilepsy may induce localized changes in G protein expression.
• Elevated Gi1α and reduced levels of other G protein subtypes are associated with increased susceptibility to maintaining seizure activity.