ATP2A1 and amyotrophic lateral sclerosis: A few notable differences identified in the differential regulation of ALS and CP FM were as follows- ATP2A1 and ATP2A2, two-muscle specific, energy demanding fast fiber SERCA pumps (sarco (endo) plasmic reticulum Ca2+ ATPase) were very strongly downregulated in ALS, suggesting a reduced efficacy in sequestering Ca2+ to the SR from the cytosol (Periasamy and Kalyanasundaram, 2007).