Expression of functional neurotransmitter receptors in Xenopus oocytes after injection of human brain membranes

Abstract

The Xenopus oocyte is a very powerful tool for studies of the structure and function of membrane proteins, e.g., messenger RNA extracted from the brain and injected into oocytes leads to the synthesis and membrane incorporation of many types of functional receptors and ion channels, and membrane vesicles from Torpedo electroplaques injected into oocytes fuse with the oocyte membrane and cause the appearance of functional Torpedo acetylcholine receptors and Cl ؊ channels. This approach was developed further to transplant already assembled neurotransmitter receptors from human brain cells to the plasma membrane of Xenopus oocytes. Membranes isolated from the temporal neocortex of a patient, operated for intractable epilepsy, were injected into oocytes and, within a few hours, the oocyte membrane acquired functional neurotransmitter receptors to ␥-aminobutyric acid, ␣-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid, kainate, and glycine. These receptors were also expressed in the plasma membrane of oocytes injected with mRNA extracted from the temporal neocortex of the same patient. All of this makes the Xenopus oocyte a more useful model than it already is for studies of the structure and function of many human membrane proteins and opens the way to novel pathophysiological investigations of some human brain disorders.

Properties of glutamate receptors of Alzheimer's disease brain transplanted to frog oocytes

“…The properties of neurotransmitter receptors microtransplanted from fresh human brain to frog oocytes are similar to those of native receptors present in brain slices (19,20). Remarkably, we find now that GABA and GluRs from postmortem brains kept frozen for Ͼ10 years are still functional and behave like the native receptors (see also ref.…”

“…Portions of the temporal cerebral cortex from the postmortem brains of 8 AD and 11 age-matched control non-AD subjects (SI Table 1) were used to prepare cell membranes according to procedures previously described (19,22). The membranes were suspended in water and kept frozen at Ϫ80°C until used for an experiment.…”

Abnormal GABA A receptors from the human epileptic hippocampal subiculum microtransplanted to Xenopus oocytes

“…Membranes were prepared as described (7,8) by using tissues from human epileptic brain regions (hippocampus and TL).…”

“…However, their role in epileptogenesis remains an open question (1,2), and the functional and anatomical correlates of TLE are areas of lively debate (3)(4)(5). To address these issues, we recently introduced the method of microtransplanting already assembled neurotransmitter receptors from the human epileptic brain to the plasma membrane of Xenopus oocytes (6)(7)(8), and we have shown that GABA A receptors, transplanted from TL epileptic brains into oocytes, display an excessive GABA A -receptor run-down, which is very similar to that of GABA currents recorded from pyramidal neurons in TL slices derived from the same patients (9,10).…”

Phosphatase inhibitors remove the run-down of γ-aminobutyric acid type A receptors in the human epileptic brain

“…Essentially, this method consists in injecting the oocytes with cell membranes prepared from foreign tissues. The oocyte plasma membrane incorporates the foreign membranes and efficiently acquires functional human neurotransmitter receptors and voltage-operated channels, which retain the properties they have in their native tissues (13)(14)(15).…”