Tristetraprolin: A cytosolic regulator of mRNA turnover moonlighting as transcriptional corepressor of gene expression

Integrated proteomics and phosphoproteomics profiling dynamic signaling networks underlying two distinct types of macrophage activation

Macrophages play a crucial role in antimicrobial host defense and those with differential maturation/differentiation status differ in inflammatory responses. Herein, GM-CSF and M-CSF primed mouse bone marrow derived macrophages (GM-BMDMs, GM and M-BMDMs, M), the well-established macrophage models in vitro, were utilized and their dynamic signaling changes in response to gram-negative bacteria component LPS treatment were analyzed using both 4D label-free proteomics and phosphoproteomics. Protein changes maintained relatively constant within or across GM and M macrophages post LPS challenge while phospho-protein exhibited more diverse and transient changes. Early induction of phospho-mediated GTPase activities, mRNA processing, and protein-mediated metabolic changes like oxidative phosphorylation (OXPHOS)/mitochondria function was identified at 1 h and maintained until 6 h post LPS treatment in GM and M while canonical TLR mediated MyD88-dependent and -independent pathways were activated at 3 and 6 h, individually at protein levels. Classical and novel phospho-sites for MyD88 and TRIF signaling pathways were also detected by phosphoproteomics. Comprehensively, the integrated protein and phospho-protein trend analysis was conducted and the core protein-phospho-protein network for the early phase actin reorganization, phagocytosis, and TLR signaling in both GM and M were presented. Taken together, these data described differences and similarities between these two types of macrophages in terms of their inflammatory responses to LPS.

Deletion of smooth muscle ZFP36 promotes neointimal hyperplasia in mice

Platelet-derived growth factor (PDGF-BB) released from the injured intima induces the proliferation and migration of vascular smooth muscle cells (VSMCs), which is the key mechanism of neointimal hyperplasia. Zinc finger 36 (ZFP36), a widespread RNA-binding protein, is important for pathological processes in many diseases. In this study we investigated the role of ZFP36 in VSMCs proliferation, migration and neointimal hyperplasia in mice. We generated smooth muscle-specific Zfp36 knockout (Zfp36SMKO) mice, and established restenosis mouse models by ligation of left carotid artery in Zfp36SMKO mice. We showed that the expression levels of ZFP36 were significantly decreased in human atherosclerotic coronary arteries and murine injured carotid arteries compared with controls. Compared to control Zfp36fl/fl mice, Zfp36SMKO mice displayed accelerated neointimal hyperplasia. In cultured mouse VSMCs, PDGF-BB (20 ng/mL) significantly downregulated ZFP36 expression through KLF4 binding site in Zfp36 promoter. We revealed that ZFP36 could bind to the mRNA of cell migration-inducing protein (CEMIP) and promoted its degradation in VSMCs, thereby reducing the expression of CEMIP protein. Knockdown of Cemip inhibited VSMCs proliferation and migration induced by Zfp36 knockout, thereby suppressing neointimal hyperplasia in Zfp36SMKO mice. We conclude that vascular smooth muscle ZFP36 has a protective effect against neointimal hyperplasia by reducing CEMIP expression. ZFP36 is downregulated by vascular injury and PDGF-BB treatment, which promotes VSMCs proliferation and migration and neointima formation. The results suggest that targeting ZFP36 may represent a novel therapeutic strategy for preventing or treating neointimal hyperplasia and related cardiovascular diseases.

Tristetraprolin affects invasion-associated genes expression and cell motility in triple-negative breast cancer model

Tristetraprolin (TTP) is an RNA-binding protein that negatively regulates its target mRNAs and has been shown to inhibit tumor progression and invasion. Tumor invasion requires precise regulation of cytoskeletal components, and dysregulation of cytoskeleton-associated genes can significantly alter cell motility and invasive capability. Several genes, including SH3PXD2A, SH3PXD2B, CTTN, WIPF1, and WASL, are crucial components of the cytoskeleton reorganization machinery and are essential for adequate cell motility. These genes are also involved in invasion processes, with SH3PXD2A, SH3PXD2B, WIPF1, and CTTN being key components of invadopodia-specialized structures that facilitate invasion. However, the regulation of these genes is not well understood. This study demonstrates that ectopic expression of TTP in MDA-MB-231 cells leads to decreased mRNA levels of CTTN and SH3PXD2A, as well as defects in cell motility and actin filament organization. Additionally, doxorubicin significantly increases TTP expression and reduces the mRNA levels of cytoskeleton-associated genes, enhancing our understanding of how doxorubicin may affect the transcriptional profile of cells. However, doxorubicin affects target mRNAs differently than TTP ectopic expression, suggesting it may not be the primary mechanism of doxorubicin in breast cancer (BC) treatment. High TTP expression is considered as a positive prognostic marker in multiple cancers, including BC. Given that doxorubicin is a commonly used drug for treating triple-negative BC, using TTP as a prognostic marker in this cohort of patients might be limited since it might be challenging to understand if high TTP expression occurred due to the favorable physiological state of the patient or as a consequence of treatment.

Ectopic expression of TTP gene from human in poplar promotes xylem differentiation and confers plant drought tolerance

The CCCH zinc finger proteins play critical roles in a wide variety of growth, development, and stress responses. Currently, limited reports are available about the roles of animal CCCH proteins in plants. In this study, we report the identification of human TTP (hTTP) with functional similarity to PdC3H17 in a hybrid poplar. hTTP and PdC3H17 shared highly similar tandem CCCH zinc-finger RNA-binding domains. The fragments excluding the CCCH domain of both hTTP and PdC3H17 possessed transcriptional activation activities in yeast cells. Compared to the controls, ectopic expression of hTTP in poplar caused dwarfism, and resulted in significant increases in stem xylem vessel number and photosynthetic and ROS-scavenging abilities, thereby enhancing plant tolerance to drought stress. Our results suggest that hTTP may perform a function in poplar through the PdC3H17-mediated system, and provide an example for the application of animal genes in plants.

ZIKV induction of tristetraprolin in endothelial and Sertoli cells post-transcriptionally inhibits IFNβ/λ expression and promotes ZIKV persistence

IMPORTANCE

Our findings define a novel role for ZIKV-induced TTP expression in regulating IFNβ/IFNλ production in primary hBMECs and Sertoli cells. These cells comprise key physiological barriers subverted by ZIKV to access brain and testicular compartments and serve as reservoirs for persistent replication and dissemination. We demonstrate for the first time that the ARE-binding protein TTP is virally induced and post-transcriptionally regulates IFNβ/IFNλ secretion. In ZIKV-infected hBMEC and Sertoli cells, TTP knockout increased IFNβ/IFNλ secretion, while TTP expression blocked IFNβ/IFNλ secretion. The TTP-directed blockade of IFN secretion permits ZIKV spread and persistence in hBMECs and Sertoli cells and may similarly augment ZIKV spread across IFNλ-protected placental barriers. Our work highlights the importance of post-transcriptional ZIKV regulation of IFN expression and secretion in cells that regulate viral access to protected compartments and defines a novel mechanism of ZIKV-regulated IFN responses which may facilitate neurovirulence and sexual transmission.

Advances in The Study of RNA-binding Proteins in Diabetic Complications

Background

It has been reported that diabetes mellitus affects 435 million people globally as a primary health care problem. Despite many therapies available, many diabetes remains uncontrolled, giving rise to irreversible diabetic complications that pose significant risks to patients’ wellbeing and survival.

Scope of Review

In recent years, as much effort is put into elucidating the posttranscriptional gene regulation network of diabetes and diabetic complications; RNA binding proteins (RBPs) are found to be vital. RBPs regulate gene expression through various post-transcriptional mechanisms, including alternative splicing, RNA export, messenger RNA translation, RNA degradation, and RNA stabilization.

Major Conclusions

Here, we summarized recent studies on the roles and mechanisms of RBPs in mediating abnormal gene expression in diabetes and its complications. Moreover, we discussed the potential and theoretical basis of RBPs to treat diabetes and its complications.

• Mechanisms of action of RBPs involved in diabetic complications are summarized and elucidated.

• We discuss the theoretical basis and potential of RBPs for the treatment of diabetes and its complications.

• We summarize the possible effective drugs for diabetes based on RBPs promoting the development of future therapeutic drugs.