map Kinases p38 and JNK are activated by the steroid hormone 1,25-(OH)2-vitamin D3 in C2C12 muscle cell line

CLAUDIA GRACIELA BUITRAGO; CAROLINA RONDA, ANA; J RUSSO, ANA; BOLAND RICARDO,

Nashville

Congreso; 27th Annual Meeting of American Society for Bone and Mineral Research; 2005

In chick skeletal muscle cell primary cultures we previously demostrated that 1a,25(OH)2-vitamin D3 [1a,25(OH)2D3], the hormonally active form of vitamin D, increases the phosphorylation and activity of the extracellular signal-regulated mitogen-activated protein (MAP) kinase isoforms ERK1 and ERK2, their subsequent translocation to the nucleus and involvement in DNA synthesis stimulation. In this study we show that other members of the MAP kinase superfamily are also activated by the hormone. Using the muscle cell line C2C12 we found that 1a,25(OH)2D3 within 1 min phosphorylates and increases the activity of p38 MAPK. The immediately upstream kinases MKK3/MKK6 were also phosphorylated by the hormone suggesting their participation in p38 activation. 1a,25(OH)2D3 was able to dephosphorylate/activate the ubiquitous cytosolic tyrosine kinase c-Src in C2C12 cells and studies with specific inhibitors imply that Src participates in hormone induced-p38 activation. Of relevance, 1a,25(OH)2D3 induced in the C2C12 line the stimulation of MAPKAP-kinase 2 and subsequent phosphorylation of HSP27 in a p38 kinase activationdependent manner. Treatment with the p38 inhibitor, SB203580, blocked p38 phosphorylation caused by the hormone and inhibit the phosphorylation of its downstrean substrates. 1a,25(OH)2D3 also promotes the phosphorylation of c-jun N-terminal protein kinases (JNK 1/2), the response is fast (0.5-1 min.) and maximal phosphorylation of the enzyme is observed at physiological doses of 1a,25(OH)2D3 (1 nM). The relative contribution of ERK-1/2, p38 and JNK-1/2 and their interrelationships in hormonal regulation of muscle cell proliferation and differentiation remain to be established.a,25(OH)2-vitamin D3 [1a,25(OH)2D3], the hormonally active form of vitamin D, increases the phosphorylation and activity of the extracellular signal-regulated mitogen-activated protein (MAP) kinase isoforms ERK1 and ERK2, their subsequent translocation to the nucleus and involvement in DNA synthesis stimulation. In this study we show that other members of the MAP kinase superfamily are also activated by the hormone. Using the muscle cell line C2C12 we found that 1a,25(OH)2D3 within 1 min phosphorylates and increases the activity of p38 MAPK. The immediately upstream kinases MKK3/MKK6 were also phosphorylated by the hormone suggesting their participation in p38 activation. 1a,25(OH)2D3 was able to dephosphorylate/activate the ubiquitous cytosolic tyrosine kinase c-Src in C2C12 cells and studies with specific inhibitors imply that Src participates in hormone induced-p38 activation. Of relevance, 1a,25(OH)2D3 induced in the C2C12 line the stimulation of MAPKAP-kinase 2 and subsequent phosphorylation of HSP27 in a p38 kinase activationdependent manner. Treatment with the p38 inhibitor, SB203580, blocked p38 phosphorylation caused by the hormone and inhibit the phosphorylation of its downstrean substrates. 1a,25(OH)2D3 also promotes the phosphorylation of c-jun N-terminal protein kinases (JNK 1/2), the response is fast (0.5-1 min.) and maximal phosphorylation of the enzyme is observed at physiological doses of 1a,25(OH)2D3 (1 nM). The relative contribution of ERK-1/2, p38 and JNK-1/2 and their interrelationships in hormonal regulation of muscle cell proliferation and differentiation remain to be established.