The cyclic AMP phosphodiesterase 4D5 (PDE4D5)/receptor for activated C-kinase 1 (RACK1) signalling complex as a sensor of the extracellular nano-environment

The roles of RACK1 in the pathogenesis of Alzheimer's disease

The receptor for activated C kinase 1 (RACK1) is a protein that plays a crucial role in various signaling pathways and is involved in the pathogenesis of Alzheimer's disease (AD), a prevalent neurodegenerative disease. RACK1 is highly expressed in neuronal cells of the central nervous system and regulates the pathogenesis of AD. Specifically, RACK1 is involved in regulation of the amyloid-β precursor protein processing through α- or β-secretase by binding to different protein kinase C isoforms. Additionally, RACK1 promotes synaptogenesis and synaptic plasticity by inhibiting N-methyl-D-aspartate receptors and activating gamma-aminobutyric acid A receptors, thereby preventing neuronal excitotoxicity. RACK1 also assembles inflammasomes that are involved in various neuroinflammatory pathways, such as nuclear factor-kappa B, tumor necrosis factor-alpha, and NOD-like receptor family pyrin domain-containing 3 pathways. The potential to design therapeutics that block amyloid-β accumulation and inflammation or precisely regulate synaptic plasticity represents an attractive therapeutic strategy, in which RACK1 is a potential target. In this review, we summarize the contribution of RACK1 to the pathogenesis of AD and its potential as a therapeutic target.

Repair of Large-Scale Rib Defects Based on Steel-Reinforced Concrete-Designed Biomimetic 3D-Printed Scaffolds with Bone-Mineralized Microenvironments

Tissue engineering technology provides a promising approach for large-scale bone reconstruction in cases of extensive chest wall defects. However, previous studies did not consider meticulous scaffold design specific to large-scale rib regeneration in terms of three-dimensional (3D) shape, proper porous structures, enough mechanical strength, and osteogenic microenvironments. Thus, there is an urgent need to develop an appropriate bone biomimetic scaffold (BBS) to address this problem. In this study, a BBS with controllable 3D morphology, appropriate mechanical properties, good biocompatibility and biodegradability, porous structure suitable for cell loading, and a biomimetic osteogenic inorganic salt (OIS) microenvironment was successfully prepared by integrating computer-aided design, 3D-printing, cast-molding, and freeze-drying technologies. The addition of the OIS in the scaffold substantially promoted ectopic bone regeneration in vivo, which might be attributed to the activation of osteogenic and angiogenic signaling pathways as well as upregulated expression of osteogenic genes. More importantly, dual long rib defects could be successfully repaired and medullary cavity recanalized by the rib-shaped mature cortical bone, which might be mediated by the activation of osteoclast signaling pathways. Thus, this paper presents a reliable BBS and proposes a new strategy for the repair of large-scale bone defects.

Inhibition of Fam114A1 protects melanocytes from apoptosis through higher RACK1 expression

Fam114A1 is a gene closely related to the development of nerve cells, melanocytes, and nerve cells that originate from the neural crest of the embryonic ectoderm. Recent studies showed that Fam114A1 has a role in the occurrence of ankylosing myelitis spondylitis and autoimmune enteritis; still, its cellular function remains poorly understood. In this study, we investigated the effect of Fam114A1 on the biological activity of melanocytes. We found that the expression of Fam114A1 in vitiligo melanocytes (MCV-L, MCV-N, PI3V) was higher than that in normal melanocytes, and the biological function of melanocytes was significantly affected when the Fam114A1 gene was silenced. Inhibition of Fam114A1 increased proliferation, migration, and melanin synthesis proteins, decreased apoptosis, while its overexpression reversed this process. Mechanistically, we discovered that RACK1 is a target protein of Fam114A1 and that RACK1 can be negatively regulated by Fam114A1. Further study showed that Fam114A1 inhibition could not protect melanocytes from apoptosis once the expression of RACK1 protein was silenced. In summary, Fam114A1 is an effective regulatory protein for regulating the function of melanocytes. Inhibition Fam114A1 protects melanocytes from apoptosis through increasing RACK1.

Quantitative Phase Imaging of Spreading Fibroblasts Identifies the Role of Focal Adhesion Kinase in the Stabilization of the Cell Rear

Cells attaching to the extracellular matrix spontaneously acquire front-rear polarity. This self-organization process comprises spatial activation of polarity signaling networks and the establishment of a protruding cell front and a non-protruding cell rear. Cell polarization also involves the reorganization of cell mass, notably the nucleus that is positioned at the cell rear. It remains unclear, however, how these processes are regulated. Here, using coherence-controlled holographic microscopy (CCHM) for non-invasive live-cell quantitative phase imaging (QPI), we examined the role of the focal adhesion kinase (FAK) and its interacting partner Rack1 in dry mass distribution in spreading Rat2 fibroblasts. We found that FAK-depleted cells adopt an elongated, bipolar phenotype with a high central body mass that gradually decreases toward the ends of the elongated processes. Further characterization of spreading cells showed that FAK-depleted cells are incapable of forming a stable rear; rather, they form two distally positioned protruding regions. Continuous protrusions at opposite sides results in an elongated cell shape. In contrast, Rack1-depleted cells are round and large with the cell mass sharply dropping from the nuclear area towards the basal side. We propose that FAK and Rack1 act differently yet coordinately to establish front-rear polarity in spreading cells.