Lysophosphatidic acid receptor signaling in mammalian retinal pigment epithelial cells.

Journal Article (Journal Article)

Purpose

Lysophosphatidic acid (LPA) is a phospholipid growth factor that stimulates proliferation, chemotaxis, cation currents, and K(+) currents in retinal pigment epithelial (RPE) cells. LPA receptor transduction was analyzed in human and rat RPE cells.

Methods

Cells were cultured with standard methods, and signaling pathways were analyzed with a variety of approaches, including whole-cell recording, calcium imaging, and second-messenger assays.

Results

LPA-activated nonselective cation currents in rat RPE were blocked by the protein tyrosine kinase (PTK) inhibitor genistein, by the MAP kinase kinase (MEK) inhibitor PD98059, and by loading cells with antibodies to G(alpha(i)/o/t/z). LPA activated the MAP kinase and extracellular signal-related kinase (ERK)-1, and produced a dose-dependent inhibition of cAMP production. LPA stimulated a dose-dependent increase in [Ca(2+)](i) that persisted in Ca(2+)-free medium and was reduced by pretreatment with thapsigargin, suggesting it involves release from intracellular stores. The [Ca(2+)](i) increase was not blocked by ryanodine or the phospholipase C inhibitor U73122. LPA did not stimulate inositol phosphate production. Similar to the cation current, LPA-evoked [Ca(2+)](i) increases were blocked by PD98059 and by loading cells with antibodies to G(alpha(i)/o/t/z). RT-PCR experiments showed the presence of RNA for three LPA receptor subtypes (Edg2, -4, and -7); RNase protection assays showed the strongest expression for Edg2 receptor RNA.

Conclusions

LPA receptors in RPE cells activate pertussis toxin (PTx)-sensitive G proteins that inhibit cAMP accumulation; stimulate MAP kinase which activates a cation current and probably contributes to mitogenesis; and stimulate release of Ca(2+) from intracellular stores that appears independent of IP(3) and ryanodine receptor activation.

Duke Authors

Cited Authors

  • Thoreson, WB; Ryan, JS; Shi, C; Kelly, ME; Bryson, EJ; Toews, ML; Ediger, TL; Chacko, DM

Published Date

  • July 2002

Published In

Volume / Issue

  • 43 / 7

Start / End Page

  • 2450 - 2461

PubMed ID

  • 12091450

Electronic International Standard Serial Number (EISSN)

  • 1552-5783

International Standard Serial Number (ISSN)

  • 0146-0404

Language

  • eng