Fig. 5. Expression of MEK5 and ERK5 in wild-type and MEK5DD transgenic mice. Lysates were prepared from wild-type (WT) and transgenic (TG) hearts, and 20 µg of protein were separated by SDS–PAGE. (A) Expression of HA-tagged MEK5DD was analyzed in different lines of transgenic mice by immunoblotting with anti-HA antibody. Lines of MEK5DD transgenic mice are indicated by identifying numbers. For each line, lysate was prepared from two hearts and loaded in adjacent lanes. Expression of (B) MEK5 and (C) ERK5 was analyzed in wild-type and line 367 MEK5DD transgenic mice by immunoblotting with L610 rabbit anti-MEK5 antiserum and rabbit anti-ERK5. Bands that are either non-specific (asterisk) or degradation products (arrowhead) are indicated. Note the reduced mobility of ERK5 in transgenic animals relative to wild type.