Sarcoglycans and GABAA Rε receptors in cerebral cortex, thalamus and hippocampus: an immunohistochemical study

Abstract

The Sarcoglycans sub-complex is a protein system which plays a role in sarcolemma stabilization, protecting the fibers by any injury provoked by muscle activity. This complex is composed by six transmembrane glycoproteins, α-,β-,γ-,δ-,ε- and ξ-sarcoglycans and, although numerous studies have been conducted on this system, there are no many data about its localization in non-muscular tissues. In our previous study we have analyzed the sarcoglycans expression and localization in rat’s cerebral cortex and our results showed that all sarcoglycans are present with a staining pattern in relation to the cerebral cortex area observed. In particular we think that they could be associated with synapse sites such as inhibitory GABA_A Rε receptors. In order to verify any association between sarcoglycans and GABA_A Rε receptors we performed double immunolabeling to detect α-,β-,γ-,δ-,ε- and ξ-sarcoglycans and GABA_A Rε receptor. Our results have shown that in cerebral cortex each sarcoglycans is equally associated with GABA_A Rε receptor, showing some point of colocalization around the cellular soma. Moreover, we observed the reaction in thalamus and hippocampus where we found that all sarcoglycans are expressed with the same “spot-like” staining pattern that we observed in cerebral cortex. Instead, in the extension of the neurons the proteins present a linear staining pattern. We have also found that in these districts the fluorescence pattern of GABA_A Rε receptor increase together with the sarcoglycans fluorescence pattern, supporting our previous idea about a tight correlation between sarcoglycans and GABA_A Rε receptors. These results suggest again a role of sarcoglycans in cellular signalling, regulating the post-synaptic receptor assembly. On this basis it could be hypothesized that sarcoglycans could be involved in some pathologies of the brain becoming, in these districts, as important as in muscle.