The Impact of Profilin-1 Mutations on Protein Homeostasis in Amyotrophic Lateral Sclerosis.

Amyotrophic lateral sclerosis (ALS) is a progressive, fatal disease characterized by the dysfunction and degeneration of motor neurons in the central nervous system. ALS has been linked to a number of genetic mutations, including point mutations in the actin-binding protein profilin-1 (Pfn1). While the prevalence of Pfn1 mutations is low, around 1% of inherited forms of the disease, an understanding of their impact on motor neuron cell death can provide insight into the mechanisms underlying ALS onset and progression. As Pfn1 is an important regulator of the actin cytoskeleton, we hypothesize that ALS-linked mutations of Pfn1 promote defects in protein homeostasis and synaptic communication. To test this hypothesis, neuronal cells were transfected with Pfn1 constructs (including wild-type, C71G, and M118V) and subjected to cellular stressors (including heat shock and sodium arsenite treatments). Immunostaining was then used to visualize and quantify differences in protein aggregation and stress granule formation. Our results have established the baseline response with the wild-type construct and indicate that there is an increase in protein aggregation as well as in the number and size of stress granules with the mutant constructs. Our ongoing studies are aimed at validating these preliminary results, and our goal is to provide mechanistic insight pertaining to Pfn1's role in ALS disease pathogenesis.