Molecular analysis of the prostacyclin receptor's interaction with the PDZ1 domain of its adaptor protein PDZK1

Review: Acetylation Mechanisms andTargeted Therapies in Cardiac Fibrosis

Cardiac fibrosis is a common pathophysiological remodeling process that occurs in a variety of cardiovascular diseases and greatly influences heart structure and function, progressively leading to the development of heart failure. However, to date, few effective therapies for cardiac fibrosis exist. Abnormal proliferation, differentiation, and migration of cardiac fibroblasts are responsible for the excessive deposition of extracellular matrix in the myocardium. Acetylation, a widespread and reversible protein post-translational modification, plays an important role in the development of cardiac fibrosis by adding acetyl groups to lysine residues. Many acetyltransferases and deacetylases regulate the dynamic alterations of acetylation in cardiac fibrosis, regulating a range of pathogenic conditions including oxidative stress, mitochondrial dysfunction, and energy metabolism disturbance. In this review, we demonstrate the critical roles that acetylation modifications caused by different types of pathological injury play in cardiac fibrosis. Furthermore, we propose therapeutic acetylation-targeting strategies for the prevention and treatment of patients with cardiac fibrosis.

Interactions of the protein tyrosine phosphatase PTPN3 with viral and cellular partners through its PDZ domain: insights into structural determinants and phosphatase activity

The human protein tyrosine phosphatase non-receptor type 3 (PTPN3) is a phosphatase containing a PDZ (PSD-95/Dlg/ZO-1) domain that has been found to play both tumor-suppressive and tumor-promoting roles in various cancers, despite limited knowledge of its cellular partners and signaling functions. Notably, the high-risk genital human papillomavirus (HPV) types 16 and 18 and the hepatitis B virus (HBV) target the PDZ domain of PTPN3 through PDZ-binding motifs (PBMs) in their E6 and HBc proteins respectively. This study focuses on the interactions between the PTPN3 PDZ domain (PTPN3-PDZ) and PBMs of viral and cellular protein partners. We solved the X-ray structures of complexes between PTPN3-PDZ and PBMs of E6 of HPV18 and the tumor necrosis factor-alpha converting enzyme (TACE). We provide new insights into key structural determinants of PBM recognition by PTPN3 by screening the selectivity of PTPN3-PDZ recognition of PBMs, and by comparing the PDZome binding profiles of PTPN3-recognized PBMs and the interactome of PTPN3-PDZ. The PDZ domain of PTPN3 was known to auto-inhibit the protein's phosphatase activity. We discovered that the linker connecting the PDZ and phosphatase domains is involved in this inhibition, and that the binding of PBMs does not impact this catalytic regulation. Overall, the study sheds light on the interactions and structural determinants of PTPN3 with its cellular and viral partners, as well as on the inhibitory role of its PDZ domain on its phosphatase activity.

Identification of targets of Twist1 transcription factor in thyroid cancer cells

CONTEXT

Anaplastic thyroid carcinoma (ATC) is one of the most aggressive human tumors. Twist1 is a basic helix-loop-helix transcription factor involved in cancer development and progression. We showed that Twist1 affects thyroid cancer cell survival and motility.

OBJECTIVE

We aimed to identify Twist1 targets in thyroid cancer cells.

DESIGN

Transcriptional targets of Twist1 were identified by gene expression profiling the TPC-Twist1 cells in comparison with control cells. Functional studies were performed by silencing in TPC-Twist1 and in CAL62 cells the top 10 upregulated genes and by evaluating cell proliferation, survival, migration, and invasion. Chromatin immunoprecipitation was performed to verify direct binding of Twist1 to target genes. Quantitative RT-PCR was applied to study the expression level of Twist1 target genes in human thyroid carcinoma samples.

RESULTS

According to the gene expression profile, the top functions enriched in TPC-Twist1 cells were cellular movement, cellular growth and proliferation, and cell death and survival. Silencing of the top 10 upregulated genes reduced viability of TPC-Twist1 and of CAL62 cells. Silencing of COL1A1, KRT7, and PDZK1 also induced cell death. Silencing of HS6ST2, THRB, ID4, RHOB, and PDZK1IP also impaired migration and invasion of TPC-Twist1 and of CAL62 cells. Chromatin immunoprecipitation showed that Twist1 directly binds the promoter of the top 10 upregulated genes. Quantitative RT-PCR showed that HS6ST2, COL1A1, F2RL1, LEPREL1, PDZK1, and PDZK1IP1 are overexpressed in thyroid carcinoma samples compared with normal thyroids.

CONCLUSIONS

We identified a set of genes that mediates Twist1 biological effects in thyroid cancer cells.

Prostacyclin analogue beraprost inhibits cardiac fibroblast proliferation depending on prostacyclin receptor activation through a TGF β-Smad signal pathway

Previous studies showed that prostacyclin inhibited fibrosis. However, both receptors of prostacyclin, prostacyclin receptor (IP) and peroxisome proliferator-activated receptor (PPAR), are abundant in cardiac fibroblasts. Here we investigated which receptor was vital in the anti-fibrosis effect of prostacyclin. In addition, the possible mechanism involved in protective effects of prostacyclin against cardiac fibrosis was also studied. We found that beraprost, a prostacyclin analogue, inhibited angiotensin II (Ang II)-induced neonatal rat cardiac fibroblast proliferation in a concentration-dependent and time-dependent manner. Beraprost also suppressed Ang II-induced collagen I mRNA expression and protein synthesis in cardiac fibroblasts. After IP expression was knocked down by siRNA, Ang II-induced proliferation and collagen I synthesis could no longer be rescued by beraprost. However, treating cells with different specific inhibitors of PPAR subtypes prior to beraprost and Ang II stimulation, all of the above attenuating effects of beraprost were still available. Moreover, beraprost significantly blocked transforming growth factor β (TGF β) expression as well as Smad2 phosphorylation and reduced Smad-DNA binding activity. Beraprost also increased phosphorylation of cAMP response element binding protein (CREB) at Ser133 in the nucleus. Co-immunoprecipitation analysis revealed that beraprost increased CREB but decreased Smad2 binding to CREB-binding protein (CBP) in nucleus. In conclusion, beraprost inhibits cardiac fibroblast proliferation by activating IP and suppressing TGF β-Smad signal pathway.