FIG. 5.

Hearts from HRC null mice have increased levels of triadin expression. Cardiac homogenates from age- and sex-matched wild-type (wt) and HRC null (ko) mice were analyzed by Western blotting with antibodies to calsequestrin (CSQ), the cardiac ryanodine receptor (RyR), phospholamban (PLB), α-tubulin, and triadin. Calsequestrin (A), ryanodine receptor (B), the pentameric form of phospholamban (C), and α-tubulin (D) levels were nearly identical in wt and ko homogenates. The similar α-tubulin levels in wild-type and HRC null homogenates confirmed that approximately equal of amounts of protein were analyzed in the two samples. In contrast to calsequestrin, ryanodine receptor, and phospholamban, triadin expression was increased in HRC knockout mouse hearts (E). Bars on the left in panels A to E depict the position of Full Range Rainbow molecular weight markers. (F) Triadin expression is significantly increased in HRC null compared to wild-type cardiac tissue (1.52 ± 0.23-fold over wild type, P = 0.0027). Triadin levels from three independent pools of cardiac extract from age- and sex-matched knockout and wild-type mice were analyzed in independent experiments, and the expression of triadin was normalized to the α-tubulin level for each independent sample. Data are expressed relative to the wild-type triadin protein level, and the P values were calculated using a two-tailed, paired t test. Error bars represent the standard error of the mean for each group.