The role of cellular prion protein in immune system.

Numerous studies have investigated the cellular prion protein (PrPC) since its discovery. These investigations have explained that its structure is predominantly composed of alpha helices and short beta sheet segments, and when its abnormal scrapie isoform (PrPSc) is infected, PrPSc transforms the PrPC, leading to prion diseases, including Creutzfeldt-Jakob disease in humans and bovine spongiform encephalopathy in cattle. Given its ubiquitous distribution across a variety of cellular types, the PrPC manifests a diverse range of biological functions, including cell-cell adhesion, neuroprotection, signalings, and oxidative stress response. PrPC is also expressed in immune tissues, and its functions in these tissues include the activation of immune cells and the formation of secondary lymphoid tissues, such as the spleen and lymph nodes. Moreover, high expression of PrPC in immune cells plays a crucial role in the pathogenesis of prion diseases. In addition, it affects inflammation and the development and progression of cancer via various mechanisms. In this review, we discuss the studies on the role of PrPC from various immunological perspectives. [BMB Reports 2023; 56(12): 645-650].

Ginsenosides are active ingredients in Panax ginseng with immunomodulatory properties from cellular to organismal levels.

The immune system is one of the most important parts of the human body and immunomodulation is the major function of the immune system. In response to outside pathogens or high inflammation, the immune system is stimulated or suppressed. Thus, identifying effective and potent immunostimulants or immunosuppressants is critical. Ginsenosides are a type of steroid saponin derived from ginseng. Most are harmless to the body and even have tonic effects. In this review, we mainly focus on the immunostimulatory and immunosuppressive roles of two types ginsenosides: the protopanaxadiol (PPD)-type and protopanaxatriol (PPT)-type. PPT-type ginsenosides include Rg1, Rg2, Rh4, Re and notoginsenoside R1, and PPD-type ginsenosides include Rg3, Rh2, Rb1, Rb2, Rc, Rd, compound K (CK) and PPD, which activate the immune responses. In addition, Rg1 and Rg6 belong to PPT-type ginsenosides and together with Rg3, Rb1, Rd, CK show immunosuppressive properties. Current explorations of ginsenosides in immunological areas are in the preliminary stages. Therefore, this review may provide some novel ideas to researchers who study the immunoregulatory roles of ginsenosides.

Involvement of Cellular Prion Protein in Invasion and Metastasis of Lung Cancer by Inducing Treg Cell Development.

The cellular prion protein (PrPC) is a cell surface glycoprotein expressed in many cell types that plays an important role in normal cellular processes. However, an increase in PrPC expression has been associated with a variety of human cancers, where it may be involved in resistance to the proliferation and metastasis of cancer cells. PrP-deficient (Prnp0/0) and PrP-overexpressing (Tga20) mice were studied to evaluate the role of PrPC in the invasion and metastasis of cancer. Tga20 mice, with increased PrPC, died more quickly from lung cancer than did the Prnp0/0 mice, and this effect was associated with increased transforming growth factor-beta (TGF-ß) and programmed death ligand-1 (PD-L1), which are important for the development and function of regulatory T (Treg) cells. The number of FoxP3+CD25+ Treg cells was increased in Tga20 mice compared to Prnp0/0 mice, but there was no significant difference in either natural killer or cytotoxic T cell numbers. In addition, mice infected with the ME7 scrapie strain had decreased numbers of Treg cells and decreased expression of TGF-ß and PD-L1. These results suggest that PrPC plays an important role in invasion and metastasis of cancer cells by inducing Treg cells through upregulation of TGF-ß and PD-L1 expression.