Fig. 1.

Expression and localization of STIM1 in rat ventricular myocytes. (A) The STIM1 protein is found in isolated ventricular myocytes (Left), in ventricular tissue (Middle), and in liver tissue (Right) by Western blot to be the same size. The total protein loaded for each lane is indicated at the bottom. (B) Immunofluorescence imaging shows the cellular distribution of STIM1 (Left) and α-actinin (Middle) in a freshly isolated ventricular myocyte. Superimposed images (Right) indicate that the STIM1 immunofluorescence is at the Z-disk, identified by α-actinin. The insets (Bottom) correspond to the area marked with the dashed white box in the upper left of each image. STIM1 appears to form puncta and line segments along the Z-disk, consistent with it being located in clusters at the jSR. (C) STIM1 immunofluorescence using anti-STIM1 antibody that was preabsorbed using STIM1-null myocytes shows that the longitudinal streaks of “STIM1 fluorescence” shown in the Left panel of B was nonspecific binding. The Inset better reveals the jSR pattern of immunofluorescence for STIM1.