Up-regulation of nuclear PLCbeta1 in myogenic differentiation.
Phospholipase C beta(1) (PLCbeta(1)) signaling in both cell proliferation and differentiation has been largely investigated, but its role in myoblast differentiation is still unclear. The C2C12 myogenic cell line has been used in this study in order to find out the role of the two subtypes of PLCbeta(1), i.e., a and b in this process. C2C12 myoblast proliferate in response to mitogens and upon mitogen withdrawal differentiates into multinucleated myotubes. We found that differentiation of C2C12 skeletal muscle cells is characterized by a marked increase in the amount of nuclear PLCbeta(1)a and PLCbeta(1)b. Indeed, treatment with insulin induces a dramatic rise of both PLCbeta(1) subtypes expression and activity, as determined by immunochemical and enzymatic assays. Immunofluorescence experiments with anti-PLCbeta(1) specific monoclonal antibody showed a low level of cytoplasmatic and nuclear staining during the initial 12 h of differentiation whilst a massive nuclear staining is appreciable in differentiating cells. The time course of PLCbeta(1) expression versus Troponin T expression clearly indicates that the increase in the amount of PLCbeta(1) takes place 24 h earlier than that of Troponin T. Moreover, the overexpression of the PLCbeta(1)M2b mutant, lacking the nuclear localization signal and entirely located in the cytoplasm, represses the formation of mature multinucleated myotube. Taken together these results suggest that nuclear PLCbeta(1) is a key player in myoblast differentiation, functioning as a positive regulator of this process.
Faenza
Irene
I
Cellular Signalling Laboratory, Department of Anatomical Science, University of Bologna, Italy.
Bavelloni
Alberto
A
Fiume
Roberta
R
Lattanzi
Giovanna
G
Maraldi
Nadir M
NM
Gilmour
R Stewart
RS
Martelli
Alberto M
AM
Suh
Pann-Ghill
PG
Billi
Anna Maria
AM
Cocco
Lucio
L
D000818:Animals; D002454:Cell Differentiation; D002460:Cell Line; D002467:Cell Nucleus / Q000201:enzymology*; D004789:Enzyme Activation; D007527:Isoenzymes / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D018482:Muscle, Skeletal / Q000166:cytology / Q000201:enzymology*; D009154:Mutation; D019913:Nuclear Localization Signals; D054799:Phospholipase C beta; D012333:RNA, Messenger / Q000096:biosynthesis; D051381:Rats; D014158:Transcription, Genetic; D010738:Type C Phospholipases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D015854:Up-Regulation
D007527:Isoenzymes; D019913:Nuclear Localization Signals; D012333:RNA, Messenger; D010738:Type C Phospholipases; D054799:Phospholipase C beta; C518035:Plcb1 protein, rat