Identification of Targets of Phosphorylation in Heart Mitochondria

Whereas most strategies in proteomics deal with changes in protein levels, posttranslational modifications often represent pathological consequences at the molecular level without changes in abundance and, therefore represent a critical phenomenon to study. The present report elucidates an approach to studying one such posttranslational modification, phosphorylation, which is an important event in a variety of signaling cascades initiated in the heart in response to physiological and pathological stimuli. Comparison of phosphorylation profiles in different conditions, including drug treatments, receptor stimulation or blockade, and so forth, may lead to identification of relevant targets of signal transduction cascades. Furthermore, it may be possible to devise similar schemes to detect the subset of proteins modified by ubiquitinylation, lipid acylation, and so forth, and to compare differential patterns. Phosphorylation of mitochondrial targets is increasingly being recognized. Mitochondria are critical targets of a number of signaling pathways and therefore it is important to develop suitable methods to detect phosphorylation of mitochondrial targets. One approach is to perform in vitro phosphorylation in a reconstituted system of cytosol and mitochondria.