Changes in biophysical characteristics of PFN1 due to mutation causing amyotrophic lateral sclerosis
Single amino acid mutations in profilin 1 (PFN1) have been found to cause amyotrophic lateral sclerosis (ALS). Recently, we developed a mouse model for ALS using a PFN1 mutation (glycine 118 to valine, G118V), and we are now interested in understanding how PFN1 becomes toxically lethal with only one amino acid substitution. Therefore, we studied mutation-related changes in the PFN1 protein and hypothesized that such changes significantly disturb its structure. Initially, we expressed and studied the purified PFN1WT and PFN1G118V proteins from bacterial culture. We found that the PFN1G118V protein has a different mean residue ellipticity, as measured by far-UV circular dichroism, accompanied by a spectral shift. The intrinsic fluorescence of PFN1G118V showed a small fluctuation in maximum fluorescence absorption and intensity. Moreover, we examined the time course of PFN1 aggregation using SDS-PAGE, western blotting, and MALDI-TOF/TOF and found that compared with PFN1WT, PFN1G118V had an increased tendency to form aggregates. Dynamic light scattering data confirmed this, showing a larger size distribution for PFN1G118V. Our data explain why PFN1G118V tends to aggregate, a phenotype that may be the basis for its neurotoxicity.
KeywordsPFN1G118V PFN1WT ALS Aggregation Actin binding domain
We gratefully acknowledge Dr. Seyed Omid Ranaei Siadat from the Protein Research Center (Shahid Beheshti University) for allowing us to access his laboratory, which focuses on protein expression. Financial support by the Shahid Beheshti University Research Council is also gratefully acknowledged. This manuscript was edited by the Science Communication Group at the University of Arkansas for Medical Sciences (UAMS); we also thank Caroline Barham (UAMS) for proofreading the manuscript. The authors acknowledge funding from the UAMS startup fund, UAMS Center for Translational Neurosciences, NIGMS IDeA Program Award P30 GM110702, P20GM109005, and NINDS NS088653 and NS101334.
M.K. introduced the idea, designed the study, analyzed the data, and wrote the manuscript. A.G. designed the study, analyzed the data, and wrote the manuscript. M.N. designed and performed experiments, analyzed data, and wrote the manuscript. P.G. assisted with MALDI analysis and helped prepare the manuscript. A.A. assisted with the expression of recombinant PFN1, and S.A. assisted with sub-cloning experiments.
Compliance with ethical standards
Conflict of interest
Dr. Kiaei and UAMS have a financial interest in the technology discussed in this publication. These financial interests have been reviewed and approved in accordance with the UAMS conflict of interest policies. Other authors have no conflict to disclose.
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