Purification and biochemical characterization of Drosophila VAP-MSP domain

Abstract

VAP-B is an integral membrane protein, located in the endoplasmic reticulum. In humans, a P56S mutation is associated with familial forms of motor neuron disease. One effect of the mutation is the aggregation of the protein, which also pulls down wild type protein into these aggregates. The exact relationship between the mutation, the protein aggregation and motor neuron disease is not well understood. In our laboratory we have generated a list of 132 genetic interactors of VAP-B using a reverse genetic screen in Drosophila. These interactors will be used to build a systems level genetic network that will be an important step in trying to understand the mechanism of Amyotrophic lateral sclerosis. In this study, we are trying to characterize the Drosophila VAP major sperm protein (MSP) domain, both wild type and mutant biophysically. We are also attempting to identify novel protein interactors of VAP wild type and VAP (P56S) in-vitro and in-vivo. We have been successful in expressing both the wild type (wt) and mutant (P58S) versions of the VAP MSP in E. coli. Transgenic lines expressing full length, Myc tagged, VAP (wt) and VAP (P58S) in the brain have been characterized. The characterization of the purified proteins and of the interactors is ongoing. We expect our studies to complement our genetic studies and help shed light on the mechanistic basis of Amyotrophic lateral sclerosis.