Wnt3a induces the expression of acetylcholinesterase during osteoblast differentiation via the Runx2 transcription factor

Abstract

Acetylcholinesterase (AChE) hydrolyzes acetylcholine to terminate cholinergic transmission in neurons. Apart from this AChE activity, emerging evidence suggests that AChE could also function in other, non-neuronal cells. For instance, in bone, AChE exists as a proline-rich membrane anchor (PRiMA)-linked globular form in osteoblasts, in which it is proposed to play a noncholinergic role in differentiation. However, this hypothesis is untested. Here, we found that in cultured rat osteoblasts, AChE expression was increased in parallel with osteoblastic differentiation. Because several lines of evidence indicate that AChE activity in osteoblast could be triggered by Wnt/β-catenin signaling, we added recombinant human Wnt3a to cultured osteoblasts and found that this addition induced expression of the gene and protein product. This Wnt3a-induced AChE expression was blocked by the Wnt-signaling inhibitor Dickkopf protein-1 (DKK-1). We hypothesized that the Runt-related transcription factor 2 (Runx2), a downstream transcription factor in Wnt/β-catenin signaling, is involved in AChE regulation in osteoblasts, confirmed by the identification of a Runx2-binding site in the gene promoter, further corroborated by ChIP. Of note, Runx2 overexpression in osteoblasts induced AChE expression and activity of the promoter tagged with the gene. Moreover, deletion of the Runx2-binding site in the promoter reduced its activity during osteoblastic differentiation, and addition of 5-azacytidine and trichostatin A to differentiating osteoblasts affected AChE expression, suggesting epigenetic regulation of the gene. We conclude that AChE plays a role in osteoblastic differentiation and is regulated by both Wnt3a and Runx2.

Erythropoietin regulates the expression of dimeric form of acetylcholinesterase during differentiation of erythroblast

“…c), as reported previously (Xu et al . ), suggesting its specificity in erythroblastic cell. The GATA‐1 cDNA was used here in transfected TF‐1 cells to increase the amount of GATA‐1.…”

“…; Xu et al . , ). The non‐cholinergic functions of AChE have been proposed in development of aforementioned tissues/cells.…”

“…Rat primary cultured osteoblasts were prepared and cultured by the method previously described (Xu et al . ).…”

“…Aside from this cholinergic function, emerging evidence suggests additional non‐enzymatic functions of AChE in different tissues (Soreq and Seidman ; Xu et al . ).…”

“…On the other hand, the regulation of AChE and its transcriptional activators in other non‐neuronal cells were also reported, for example, osteoblast (Xu et al . , ).…”