SDF-1 controls pituitary cell proliferation through the activation of ERK1/2 and the Ca2+-dependent, cytosolic tyrosine kinase Pyk2.
Stromal cell-derived factor-1 (SDF-1) is a chemokine of the CXC subfamily that exerts its effects via CXCR4, a G-protein-coupled receptor. CXCR4 is often expressed by tumor cells, and its activation causes tumor cell proliferation. Using GH4C1 cells, here we show that SDF-1 induced cell proliferation in a dose-dependent manner. Thus, we evaluated the intracellular signaling involved in this effect. SDF-1 increased cytosolic [Ca2+] and activated Pyk2, ERK1/2, and BKCa channels. To correlate these intracellular effectors with the proliferative activity of SDF-1, we inhibited their activity using BAPTA-AM (Ca2+ chelator), PD98059 (MEK inhibitor), salicylate (Pyk2 inhibitor), and TEA (K+ channel blocker). All these compounds reverted SDF-1-induced proliferation, suggesting the involvement of multiple intracellular pathways. To identify a possible crosstalk and a molecular ordering among these pathways, we tested these antagonists on SDF-1-dependent activation of ERK1/2, Pyk2, and BKCa channels. We report that the inhibition of [Ca2+]i increase or the blockade of BKCa channel activity did not affect ERK1/2 activation by SDF-1; Pyk2 activation was purely Ca2+-dependent, not involving ERK1/2 or BKCa channels; and BKCa channel activity was antagonized by Pyk2 but not by ERK1/2 inhibitors. These data suggest that SDF-1-dependent increase of [Ca2+]i activates Pyk2, which, in turn, regulates BKCa channel activity. Conversely, ERK1/2 activation is an independent phenomenon. In conclusion, we demonstrate that SDF-1 induces proliferation of GH4C1 cells, suggesting that the activation of CXCR4 may represent a novel regulatory mechanism for pituitary cell proliferation which may contribute to pituitary adenoma development.
Massa
Alessandro
A
Section of Pharmacology, Department of Oncology, Biology, and Genetics, University of Genova, Viale Benedetto XV, 2, 16132 Genova, Italy.
Casagrande
Silvia
S
Bajetto
Adriana
A
Porcile
Carola
C
Barbieri
Federica
F
Thellung
Stefano
S
Arena
Sara
S
Pattarozzi
Alessandra
A
Gatti
Monica
M
Corsaro
Alessandro
A
Robello
Mauro
M
Schettini
Gennaro
G
Florio
Tullio
T
D000236:Adenoma / Q000201:enzymology / Q000378:metabolism / Q000473:pathology; D002118:Calcium / Q000378:metabolism; D002460:Cell Line; D049109:Cell Proliferation; D054377:Chemokine CXCL12; D019743:Chemokines, CXC / Q000502:physiology*; D004789:Enzyme Activation; D051418:Focal Adhesion Kinase 2 / Q000378:metabolism*; D019204:GTP-Binding Proteins / Q000378:metabolism; D006801:Humans; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism*; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism*; D010911:Pituitary Neoplasms / Q000201:enzymology / Q000378:metabolism / Q000473:pathology*; D020133:Reverse Transcriptase Polymerase Chain Reaction
C515255:CXCL12 protein, human; D054377:Chemokine CXCL12; D019743:Chemokines, CXC; D051418:Focal Adhesion Kinase 2; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D019204:GTP-Binding Proteins; D002118:Calcium