Figure 2.

Arginine-rich dipeptide repeat proteins (DRPs) increase mouse spinal cord x neuroblastoma hybrid (NSC-34) cell LDH release in a significant, dose-dependent manner. NSC-34 cells were treated with DRPs at doses ranging from 10 nM to 3 μM for 24 h. % LDH release was calculated based on absorbance (450 nm) values detecting the release of lactate dehydrogenase (LDH) from cells, where 0% LDH release reflects a negative control of untreated NSC-34 cells, and 100% LDH release reflects a positive control of lysed NSC-34 cells. Nearly identical dose-response curves were observed in poly-glycine-arginine (GR₁₅) (blue, EC₅₀ = 50.49 ± 25.5 nM) and poly-proline-arginine (PR₁₅) (red, EC₅₀ = 55.54 ± 20.1 nM)-treated NSC-34 cells. EC₅₀ values indicate arginine-rich DRPs to be at least 10 times more potent than non-arginine-rich DRPs. Dimethyl Sulfoxide (DMSO)-treated values (gray) represent cells that were treated with the same amount of DMSO that cells treated with DRPs dissolved in DMSO were exposed to at each dose. **** denotes p < 0.0001 (comparing DRP-treated values at each dose to DMSO-treated values at each dose by one-way ANOVA analysis of variance followed by Dunnett’s test). Data are presented as mean values ± standard deviations (error bars). N = 3 replicates per condition.