Phospholipase A2 activating protein is required for 1α,25-dihydroxyvitamin D3 dependent rapid activation of protein kinase C via Pdia3

Maryam Doroudi, Zvi Schwartz, Barbara D. Boyan

Research output: Contribution to journalArticle

22 Scopus citations

Abstract

1α,25-Dihydroxyvitamin D3 (1,25D3) regulates musculoskeletal cells via two different mechanisms: vitamin D receptor (VDR)-dependent gene transcription and rapid membrane-signaling via VDR as well as protein disulfide isomerase, family A, member 3 (Pdia3). In chondrocytes from the costochondral cartilage growth zone (GC), ligand binding to Pdia3 causes a rapid increase in phospholipase A2 (PLA2) activity leading to release of arachidonic acid and formation of lysophospholipid (LPL). LPL activates phospholipase C (PLC), and resulting inositol trisphosphate (IP 3) and diacylglycerol contribute to PKCα activation and downstream activation of ERK1/2. PLA2 activating protein (PLAA) is increased in the growth zone of rat growth plates suggesting that it mediates the 1,25D3-dependent pathway. This study examined the role of PLAA in mediating 1,25D3-dependent PKC activation using GC cells and MC3T3-E1 wild-type and PLAA-silenced osteoblasts as models. PLAA, Pdia3, and caveolin-1 (Cav-1) were detected in plasma membranes and caveolae of GC and MC3T3-E1 cells. Pdia3-immunoprecipitated samples were positive for PLAA only after 1,25D3 treatment. Cav-1 was detected when immunoprecipitated with anti-Pdia3 and anti-PLAA in both vehicle and 1,25D3 treated cells. These observations were confirmed by immunohistochemistry. 1,25D3 failed to activate PLA2 and PKC or cause PGE2 release in PLAA-silenced cells. PLAA-antibody successfully blocked the PLAA protein and consequently suppressed PKC activity in GC and MC3T3-E1 cells. Crosslinking studies confirmed the localization of PLAA on the extracellular face on the plasma membrane in untreated MC3T3-E1 cells. Taken together, our results suggest that PLAA is an important mediator of 1α,25(OH)2D3 rapid membrane mediated signaling. 1α,25(OH)2D3 likely causes conformational changes bringing Pdia3 into proximity with PLAA, and aiding in transducing the signal from caveolae to the plasma membrane.

Original languageEnglish (US)
Pages (from-to)48-56
Number of pages9
JournalJournal of Steroid Biochemistry and Molecular Biology
Volume132
Issue number1-2
DOIs
Publication statusPublished - Oct 1 2012

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Keywords

  • 1α,25(OH)D-dependent protein kinase C
  • Growth plate chondrocytes
  • MC3T3-E1 osteoblasts
  • Phospholipase A2 activating protein
  • Protein-disulfide isomerase family A, member 3

ASJC Scopus subject areas

  • Endocrinology, Diabetes and Metabolism
  • Biochemistry
  • Molecular Medicine
  • Molecular Biology
  • Endocrinology
  • Clinical Biochemistry
  • Cell Biology

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