HSPA5 and amyotrophic lateral sclerosis: Immunofluorescence of ALS motor neuron cultures revealed a significant up-regulation of the ER stress markers, binding immunoglobulin protein (BiP) and phosphoeukaryotic initiation factor 2α (pEIF2α) compared to control motor neurons (Fig. 4a, c, middle panel, P < 0.05 and P < 0.001, respectively).