Calumenin is a secretory pathway protein regulating different endoplasmic reticulum (ER) proteins such as the sarco-endoplasmic reticulum calcium ATPase (SERCA) pumps. Combined with its diverse cellular distribution, its calcium-binding ability, and its interaction with proteins involved in calcium signaling, it is easy to speculate on future description of important roles of calumenin in calcium homeostasis in many cell types, as it was initially observed in muscle cells. In this chapter, we describe basic techniques to modulate calumenin expression and detect its impact on ER calcium content using classic transfection and Western blot techniques, as well as ER calcium measurement using microplate reader.