engleski

A single mutation to cysteine near the C-terminus in alfa/beta-fold protein family causes endoplasmic reticulum retention

A Cys to Arg mutation in the extracellular domain of neuroligin-3 (NL3) was recently found in a twin set with autism. The Cys substitution led to specific retention of the mutated NL3 into the endoplasmic reticulum (ER). NL3, butyrylcholinesterase (BuChE), and acetylcholinesterase (AChE), as members of the alfa/beta-hydrolase fold family of proteins, share over 30% of amino acid identity in their extracellular domains. In particular, Arg451 in NL3 is conserved in the alfa/beta-hydrolase fold at the homologous to Arg386 in BuChE and Arg395 in AChE. A Cys substitution at the homologous Arg in the BuChE was found studying post-succinylcholine apnea in an Australian population. We have made the homologous mutation in the mouse AChE and BuChE genes and studied the expression, activity and sub-cellular localization of the mutated proteins in HEK293 cells. We found that the Arg to Cys mutations, as observed for NL3, resulted in ER retention of the proteins. Our data also indicate that the ER-retained protein was enzymatically active with catalytic constants nearly identical to the wild type enzyme. We demonstrate here that the Arg to Cys mutations result in identical alterations in the cellular phenotype alfa/beta-hydrolase fold family proteins. This finding suggests that this specific residue when modified to cysteine influences the processing and secretion of proteins in the alfa/beta-hydrolase fold family.

acetylcholinesterase; butyrylcholinesterase; neuroligin; cystein mutation

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