Tribbles-1 expression and its function to control inflammatory cytokines, including interleukin-8 levels are regulated by miRNAs in macrophages and prostate cancer cells

The pseudokinase TRIB1 controls cell function in a range of contexts, by regulating MAP kinase activation and mediating protein degradation via the COP1 ubiquitin ligase. TRIB1 regulates polarization of macrophages and dysregulated Trib1 expression in murine models has been shown to alter atherosclerosis burden and adipose homeostasis. Recently, TRIB1 has also been implicated in the pathogenesis of prostate cancer, where it is often overexpressed, even in the absence of genetic amplification. Well described TRIB1 effectors include MAP kinases and C/EBP transcription factors, both in immune cells and in carcinogenesis. However, the mechanisms that regulate TRIB1 itself remain elusive. Here, we show that the long and conserved 3’untranslated region (3’UTR) of TRIB1 is targeted by miRNAs in macrophage and prostate cancer models. By using a systematic in silico analysis, we identified multiple “high confidence” miRNAs potentially binding to the 3’UTR of TRIB1 and report that miR-101-3p and miR-132-3p are direct regulators of TRIB1 expression and function. Binding of miR-101-3p and miR-132-3p to the 3’UTR of TRIB1 mRNA leads to an increased transcription and secretion of interleukin-8. Our data demonstrate that modulation of TRIB1 by miRNAs alters the inflammatory profile of both human macrophages and prostate cancer cells

Molecular Crowding – (in Cell Culture)

Macromolecular crowding (MMC) is an intrinsic and ubiquitous feature in biological cells. We find MMC in the first bacterial cell and see it culminating in the intricate extracellular matrix (ECM) that evolved in multicellular organisms. Research work on MMC started with the observation that biological cellular systems are crammed with macromolecules. The interior of cells is teeming with enzymes, transport systems, and nucleotide assemblies. In addition, eukaryotic cells possess a three-layered cytoskeleton adding confinement to an already packed cytoplasm. Likewise, the extracellular space of multicellular organisms comprises an ECM consisting of fibrillar proteins, such as collagen or elastin, surrounded by an amorphous gel-like ground substance glycoproteins and proteoglycans and their hydration shells. Together, they provide mechanical resilience to the tissues of vertebrates while forming a crowded and structural microenvironment that in turn creates confinement for other macromolecules. Surprisingly, most biochemical and cell culture experiments are still done in non-crowded, highly aqueous solutions. Here, we shall discuss the shortcomings of contemporary cell culture and emphasize the benefits of applying MMC to cell culture models of tissues. MMC can be achieved by adding water-soluble macromolecules to the culture medium. Not only is this technically feasible, it also moves in vitro biology toward a higher physiological level, allowing the design of more meaningful cell-based assays and enabling tissue engineering of matured and physiologically relevant tissue-like assemblies