Chemokine signaling in development and disease

3-Econsystems: MicroRNAs, Receptors, and Latent Viruses; Some Insights Biology Can Gain from Economic Theory

This mini-review describes three biological systems. All three include competing molecules and a limiting molecule that binds the competing molecules. Such systems are extensively researched by economists. In fact, the issue of limited resources is the defining feature of economic systems. Therefore, we call these systems "econsystems." In an econsystem, the allocation of the limiting molecule between the competing molecules determines the behavior of the system. A cell is an example of an econsystem. Therefore, a change in the allocation of a limiting molecule as a result of, for instance, an abnormal change in the concentration of one of the competing molecules, may result in abnormal cellular behavior, and disease. The first econsystem described in this mini-review includes a long non-coding RNA and a messenger RNA (lncRNA and mRNA). The limiting molecule is a microRNA (miRNA). The lncRNA and mRNA are known as competing endogenous RNAs (ceRNAs). The second econsystem includes two receptors, and the limiting molecule is a ligand. The third econsystem includes a cis-regulatory element of a latent virus and that of a human gene. The limiting molecule is a transcription complex that binds both cis-elements.

Molecular Pharmacology of Chemokine Receptors

Chemokine receptors are involved in various pathologies such as inflammatory diseases, cancer, and HIV infection. Small molecule and antibody-based antagonists have been developed to inhibit chemokine-induced receptor activity. Currently two small molecule inhibitors targeting CXCR4 and CCR5 are on the market for stem cell mobilization and the treatment of HIV infection, respectively. Antibody fragments (e.g., nanobodies) targeting chemokine receptors are primarily orthosteric ligands, competing for the chemokine binding site. This is opposed by most small molecules, which act as allosteric modulators and bind to the receptor at a topographically distinct site as compared to chemokines. Allosteric modulators can be distinguished from orthosteric ligands by unique features, such as a saturable effect and probe dependency. For successful drug development, it is essential to determine pharmacological parameters (i.e., affinity, potency, and efficacy) and the mode of action of potential drugs during early stages of research in order to predict the biological effect of chemokine receptor targeting drugs in the clinic. This chapter explains how the pharmacological profile of chemokine receptor targeting ligands can be determined and quantified using binding and functional experiments.

Chapter One - Ubiquitination and Deubiquitination of G Protein-Coupled Receptors

The seven-transmembrane containing G protein-coupled receptors (GPCRs) constitute the largest family of cell-surface receptors. Transmembrane signaling by GPCRs is fundamental to many aspects of physiology including vision, olfaction, cardiovascular, and reproductive functions as well as pain, behavior and psychomotor responses. The duration and magnitude of signal transduction is tightly controlled by a series of coordinated trafficking events that regulate the cell-surface expression of GPCRs at the plasma membrane. Moreover, the intracellular trafficking profiles of GPCRs can correlate with the signaling efficacy and efficiency triggered by the extracellular stimuli that activate GPCRs. Of the various molecular mechanisms that impart selectivity, sensitivity and strength of transmembrane signaling, ubiquitination of the receptor protein plays an important role because it defines both trafficking and signaling properties of the activated GPCR. Ubiquitination of proteins was originally discovered in the context of lysosome-independent degradation of cytosolic proteins by the 26S proteasome; however a large body of work suggests that ubiquitination also orchestrates the downregulation of membrane proteins in the lysosomes. In the case of GPCRs, such ubiquitin-mediated lysosomal degradation engenders long-term desensitization of transmembrane signaling. To date about 40 GPCRs are known to be ubiquitinated. For many GPCRs, ubiquitination plays a major role in postendocytic trafficking and sorting to the lysosomes. This chapter will focus on the patterns and functional roles of GPCR ubiquitination, and will describe various molecular mechanisms involved in GPCR ubiquitination.

Wnt/β-catenin pathway is required for epithelial to mesenchymal transition in CXCL12 over expressed breast cancer cells

CXCL12 is positively associated with the metastasis and prognosis of various human malignancies. Cancer-associated fibroblasts (CAFs), the main cells secreting CXCL12, are capable of inducing epithelial to mesenchymal transition (EMT) of breast cancer cells. However, it has not been completely understood whether CXCL12 is involved in EMT of breast cancer cells and the underlying mechanisms. The present study aimed to investigate the effects of CXCL12 on the EMT and cancer stem cell (CSC)-like phenotypes formation by transfecting pEGFP-N1-CXCL12 plasmid into MCF-7 cells. Real time-PCR and Western blot analysis demonstrated the successful over expression of CXCL12 in MCF-7 cells. Cell counting kit-8 assay, wound healing assay and Transwell invasion analysis confirmed that over expression of CXCL12 significantly promoted the proliferation, migration and invasion in MCF-7 cells (P<0.05). In addition, ALDH activity was dramatically enhanced compared with parental (P<0.001), accompanied by the notably elevated mRNA and protein levels of OCT-4, Nanog, and SOX2 in CXCL12 overexpressed-MCF-7 cells (P<0.001). Furthermore, we observed the down regulation of E-cadherin and up regulation of vimentin, N-cadherin, and α-SMA in CXCL12 overexpressed-MCF-7 cells (P<0.01). Meanwhile, western blot and immunofluorescence assay showed that over expression of CXCL12 activated Wnt/β-catenin pathway to induce EMT of MCF-7 cells, as evidenced by the increased expression of E-cadherin after silencing β-catenin by siRNA interference (P<0.001). Collectively, our findings suggested that over expression of CXCL12 could trigger EMT by activating Wnt/β-catenin pathway and induce CSC-like phenotypes formation to promote the proliferation and metastasis in MCF-7. Hence, CXCL12 may become a promising candidate for breast cancer therapy.