Induction of Early Growth Response Gene Egr2 by Basic Calcium Phosphate Crystals through a Calcium-Dependent Protein Kinase C-Independent p44/42 Mitogen-Activated Protein Kinase Pathway

Abstract

Using the reverse transcriptase-polymerase chain reaction we examined the effect of basic calcium phosphate (BCP) crystals on the induction of the early growth response gene Egr2 transcription and the signal transduction pathway involved. The results showed that BCP crystals induced Egr2 transcription up to 8-fold, peaking at 24 h after treatment. The induction of Egr2 was confirmed by transient transfection assays using an Egr2 promoter/luciferase reporter construct and could be inhibited by the p44/42 mitogen-activated protein kinase (MAPK)-specific inhibitor U0126, or by calcium chelator TMB-8, but not by the SAPK2/p38 MAPK inhibitor SB202190 or by the protein kinase C inhibitor bisindolylmaleimide I (Bis-I). Using the Mercury Pathway Profiling System (Clontech, Palo Alto, Calif., USA) we further showed that induced Egr2 could stimulate the activities of several transcription factors that are associated with cell proliferation, such as c-fos, SRF and c-myc.

Biological Effects of Phosphate on Fibroblast-Like Synoviocytes

“…The finding that phosphate stimulated the expression of MMP1, MMP3, IL-1β, and Cox-2 suggests that phosphate, similar to calcium phosphate crystals, may play a role in the progression of OA. Previous studies found that calcium phosphate crystals stimulated the expression of egr-1 and egr-2 [28,32]. In this study, we found that phosphate had no effect on the expression of egr-2 and suppressed the expression of egr-1 in hTERT-OA 13A FLS.…”

“…of MMP1, MMP3, and IL-1β in a dose-dependent manner. However, unlike BCP crystals [28], NaH 2 PO 4 had no effect on the expression of early growth response-2 (egr-2). We also examined the expression of MMP1, cyclooxygenase-2 (Cox-2), and early growth response-1 (egr-1) in both hTERT-OA 13A FLS and hTERT-RA 516 FLS.…”

A Sodium Zinc Exchange Mechanism Is Mediating Extrusion of Zinc in Mammalian Cells

“…The effect of CaPO 4 precipitates on the induction of proteins is well documented in many cell types and numerous papers (38 -40). Application of these precipitates has a profound effect, activating the MAP kinase pathway, proto-oncogenes such as c-fos and c-jun and the nuclear transcription factor CREB (41,42). All these proteins are partially responsible for induction of gene expression and therefore may play a role also in the induction of the gene involved in Na ϩ /Zn 2ϩ exchange activity (43).…”

Biologic effects of calcium-containing crystals

“…EGR proteins serve as sensors of extracellular signaling pathways that play key roles in regulating cell proliferation, differentiation, and function. Recently, Zeng et al [40] showed that BCP crystals could induce the message levels of EGR-1 and EGR-3, which peaked at approximately 1 hour. By contrast, the message level of EGR-2 increased steadily and peaked 24 hours after BCP crystal stimulation.…”