The expression pattern of PKC theta in satellite cells of normal and regenerating muscle in the rat

Protein kinase C (PKC) is a key enzyme in regulating a variety of cellular functions. PKC theta is the most abundant PKC isoform expressed in skeletal muscle. However, the functional role of PKC theta linked to muscle regeneration has not yet been identified. Using reverse transcription (RT)-PCR and immunofluorescence analysis, we investigated the expression patterns of PKC theta in normal and regenerating tibialis anterior (TA) muscles in the rat. The amount of PKC theta mRNA in the muscle increased from the 4th to 6th post-surgical day. Immunofluorescence revealed PKC theta protein in quiescent satellite cells identified by c-Met. PKC theta immunoreactivity was not observed in many proliferating satellite cells by labeling with BrdU in the regenerating muscle. At 4, 6 and 10 days postsurgery, PKC theta immunoreactivity was observed in half the differentiating satellite cells labeling with myogenin. After 4 and 6 days, the localization of PKC theta coincided with those of Pax7 and TGF-beta. Thus, PKC theta may play an important role in inhibiting differentiation and maintaining the quiescent satellite cells in muscle regeneration.