Extracellular ATP stimulates the early growth response protein 1 (Egr-1) via a protein kinase C-dependent pathway in the human osteoblastic HOBIT cell line.
Extracellular nucleotides exert an important role in controlling cell physiology by activating intracellular signalling cascades. Osteoblast HOBIT cells express P2Y(1) and P2Y(2) G-protein-coupled receptors, and respond to extracellular ATP by increasing cytosolic calcium concentrations. Early growth response protein 1 (Egr-1) is a C(2)H(2)-zinc-finger-containing transcriptional regulator responsible for the activation of several genes involved in the control of cell proliferation and apoptosis, and is thought to have a central role in osteoblast biology. We show that ATP treatment of HOBIT cells increases Egr-1 protein levels and binding activity via a mechanism involving a Ca(2+)-independent protein kinase C isoform. Moreover, hypotonic stress and increased medium turbulence, by inducing ATP release, result in a similar effect on Egr-1. Increased levels of Egr-1 protein expression and activity are achieved at very early times after stimulation (5 min), possibly accounting for a rapid way for changing the osteoblast gene-expression profile. A target gene for Egr-1 that is fundamental in osteoblast physiology, COL1A2, is up-regulated by ATP stimulation of HOBIT cells in a timescale that is compatible with that of Egr-1 activation.
Dipartimento di Biochimica, Biofisica e Chimica delle Macromolecole, Università degli Studi di Trieste, via Giorgieri 1, 34127 Trieste, Italy.
Alex
A
Pines
Milena
M
Romanello
Laura
L
Cesaratto
Giuseppe
G
Damante
Luigi
L
Moro
Paola
P
D'andrea
Gianluca
G
Tell
D000255:Adenosine Triphosphate / Q000494:pharmacology*; D001483:Base Sequence; D002460:Cell Line; D003094:Collagen / Q000235:genetics; D024042:Collagen Type I; D017931:DNA Primers; D004268:DNA-Binding Proteins / Q000378:metabolism*; D051766:Early Growth Response Protein 1; D024202:Electrophoretic Mobility Shift Assay; D006801:Humans; D017874:Immediate-Early Proteins; D010006:Osteoblasts / Q000187:drug effects* / Q000201:enzymology / Q000378:metabolism; D011493:Protein Kinase C / Q000378:metabolism*; D013314:Stress, Mechanical; D014157:Transcription Factors / Q000378:metabolism*
D024042:Collagen Type I; D017931:DNA Primers; D004268:DNA-Binding Proteins; C497325:EGR1 protein, human; D051766:Early Growth Response Protein 1; D017874:Immediate-Early Proteins; D014157:Transcription Factors; D000255:Adenosine Triphosphate; D003094:Collagen; D011493:Protein Kinase C