Lysophosphatidic acid cooperates with EGF in inducing branching morphogenesis of embryonic mouse salivary epithelium.
Epithelial morphogenesis is supported by diffusible growth factors and by nondiffusible cell substrata, such as laminin and fibronectin. When embedded in a laminin-rich basement-membrane substratum, embryonic mouse submandibular epithelium undergoes cell proliferation and branching morphogenesis in response to epidermal growth factor (EGF) in mesenchyme-free culture but not in serum-free medium. In this study, we sought to identify the biologically active factor in serum. As this factor was heat-stable and trypsin-resistant, the lipid fraction was analyzed. Horse serum was fractionated by ethanol extraction, Folch partition with chloroform-methanol-water, and high-performance liquid chromatography, and we tested the branch-inducing activity of each fraction. We also analyzed the partially purified fraction with a mass spectrometer, indicating that the active fraction largely consisted of lysophosphatidyl-hexose. Finally we identified the molecule as lysophosphatidic acid (LPA), because, whereas lysophosphatidyl-inositol had only a slight branch-inducing activity, its relevant LPA fully substituted for serum and induced branching morphogenesis in cooperation with EGF. LPA receptor genes were expressed in submandibular epithelial cells. DNA-synthesizing cells were abundant only when cultured in the presence of both EGF and LPA, but not either singly.
Noguchi
Yohei
Y
Department of Life and Earth Sciences, Graduate School of Science and Technology, Chiba University, Chiba, Japan.
Okamoto
Atsushi
A
Kasama
Takeshi
T
Imajoh-Ohmi
Shinobu
S
Karatsu
Takashi
T
Nogawa
Hiroyuki
H
D000818:Animals; D049109:Cell Proliferation / Q000187:drug effects; D004247:DNA / Q000096:biosynthesis; D004815:Epidermal Growth Factor / Q000494:pharmacology*; D004848:Epithelium / Q000187:drug effects / Q000196:embryology / Q000378:metabolism; D006358:Hot Temperature; D050356:Lipid Metabolism; D008246:Lysophospholipids / Q000494:pharmacology*; D051379:Mice; D008813:Mice, Inbred ICR; D009024:Morphogenesis / Q000187:drug effects*; D049368:Receptors, Lysophosphatidic Acid / Q000235:genetics; D012469:Salivary Glands / Q000166:cytology / Q000187:drug effects* / Q000196:embryology* / Q000378:metabolism; D014357:Trypsin / Q000378:metabolism
D008246:Lysophospholipids; D049368:Receptors, Lysophosphatidic Acid; C025449:lysophosphatidylinositol; D004815:Epidermal Growth Factor; D004247:DNA; D014357:Trypsin; C032881:lysophosphatidic acid