CD44 induced enhancement of phosphatase activity and calcium influx: Modifications of EGR-1 expression and cell proliferation

Abstract

The purpose of this study was to investigate how CD44 impaired Akt phosphorylation, EGR-1 expression and cell proliferation. E6.1 Jurkat cells, which lack endogenous CD44 expression, were engineered to express CD44. Previously we showed that Akt is hypophosphorylated, EGR-1 expression is reduced and proliferation is impaired in CD44 expressing E6.1 Jurkat cells. The cell cycle was studied using flow cytometry and the role of calcium (Ca2+) in Akt phosphorylation and EGR-1 expression was investigated using Western blotting. Phosphatase activity was assessed using a commercially available kit. CD44 expressing cells showed disruption at the G1 to S transition. Chelation of Ca2+ from the culture media impaired Akt phosphorylation and EGR-1 expression in both CD44 expressing cells and the open vector control. Moreover, Ni2+ disrupted cell proliferation in both cell types suggesting Ca2+ import through calcium release activated calcium channels (CRAC). Staining of cells with fura-2 AM showed significantly higher Ca2+ in CD44 expressing cells as compared with the vehicle control. Finally, non-calcium mediated phosphatase activity was significantly greater in CD44 expressing cells. We propose that the enhanced phosphatase activity in the CD44 cells increased the dephosphorylation rate of Akt; at the same time, the increased intracellular concentration of Ca2+ in the CD44 cells ensured that the phosphorylation of Akt remains intact albeit at lower concentrations as compared with the vector control. Reduced Akt phosphorylation resulted in lowered expression of EGR-1 and hence, reduced the cell proliferation rate.

Role of CD44 in Regulating TLR2 Activation of Human Macrophages and Downstream Expression of Proinflammatory Cytokines

“…Inhibition of PP2A by okadaic acid resulted in increased nuclear translocation of NFκB and AP-1 and IL-1β expression in THP-1 macrophages (46). Additionally, CD44 engagement was shown to increase intracellular PP2A (47). In our work, HA suppressed NFκB p65 subunit nuclear translocation in response to TLR2 activation, and that effect was shown to be CD44 dependent as HA failed to demonstrate an anti-inflammatory effect in response to TLR2 activation in macrophages following CD44 knockdown.…”

Angelica sinensis polysaccharide inhibits proliferation, migration, and invasion by downregulating microRNA‐675 in human neuroblastoma cell line SH‐SY5Y

“…We next found AP could effectively downregulate the expressions of lncRNA‐H19 and miR‐675. CD44 is a type I transmembrane glycoprotein that participates in multiple biological processes, including proliferation, migration, and invasion (Racine et al, ; Senbanjo and Chellaiah, ). Different from the carcinogenetic roles of CD44 in cancer cells, CD44 expression is correlated with better prognosis of neuroblastoma (Combaret et al, ).…”

miR‑let‑7c‑3p targeting on Egr‑1 contributes to the committed differentiation of leukemia cells into monocyte/macrophages

“…In tumor cells, the role of Egr-1 is more complex and can be expressed as an oncogene or tumor suppressor gene in different types of tumor, for example, Egr-1 promotes the malignant behaviors of LC cells (24), circCSPP1-miR-520h-Egr-1 activation axis lead to the progression of prostate tumor (25), and Egr-1 as a potential oncogene that promotes cell proliferation and defines Egr-1 as a new molecular target in DLBCL non-Hodgkin lymphomar (26). As far as proliferation and differentiation of leukemia cells are concerned, although there are some studies associating it with the inhibition of proliferation and induction of differentiation of leukemia cells (27,28), its role in the committed differentiation of leukemia cells into monocyte/macrophages is rarely reported. micro (mi)RNAs are non-coding small RNAs with post-transcriptional regulation.…”