Download We investigated the role of GTP as inducer of differentiation in

THE
ROLE
OF
EXTRACELLULAR
GTP
ON
DIFFERENTIATION OF C2C12 MYOBLASTS.
T.Pietrangelo, R.Mancinelli, S.Fulle and G.Fanò
Istituto Interuniversitario di Miologia, Centro Studi per
l’Invecchiamento (Ce.S.I.)- Lab. Fisiologia Cellulare, Dip. Scienze
del Farmaco - Università “G. d’Annunzio” Chieti-Pescara
In our previous study we characterized the effect of extracellular
guanosine 5’ triphosphate (GTP) on Ca2+ homeostasis of mouse
skeletal muscle cell line C2C12 via specific binding sites for GTP on
plasma-membrane (Pietrangelo et al., JMRCM 23:107, 2002). GTP,
500M, is able to increase [Ca2+]i and hyperpolarize the myoblats
via intermediate Ca2+-activated K+ channels IK (Pietrangelo et al
FENS, 2002). The differentiation of C2C12 cells is characterised by
proliferation before the establishment of the postmitotic state
(myogenin and p21 dependent, respectively) followed by the
expression of myosin heavy chain (MHC) proteins and cell fusion
(Andres V. and Walsh K., JCB 132:657, 1996). In this study we
investigated the role of extracellular 500M GTP during C2C12
differentiation. Our data indicate that the presence of GTP in the
differentiation medium (DM) was able to accelerate mitoses and then
increase the number of cells expressing MHC proteins. The
incubation with both 200 nM CTX, a known blocker of IK channels,
and 500M GTP counteracts the myogenic GTP action. The cells
differentiated in presence of 500 M GTP for 4 and 24 hours reveal
different up-regulated genes, as Pax7 and MyoD, and many others
genes according to C2C12 gene expression profile during
differentiation (Moran et al, JPhysGen 10:103, 2002). Moreover, the
cells differentiated in presence of GTP were able to anticipate the
physiological responsiveness to pharmacological agonists like
nicotine or caffeine. Considering all together the data presented here,
we suggest that the specific GTP-binding sites on C2C12 cell
membranes is capable to accelerate the myogenesis via Ca2+correlated transcriptional factors.