Sorting nexin 6 enhances lamin a synthesis and incorporation into the nuclear envelope

Lamin A/C: Function in Normal and Tumor Cells

Simple Summary

The aim of this review is to summarize lamin A/C’s currently known functions in both normal and diseased cells. Lamin A/C is a nuclear protein with many functions in cells, such as maintaining a cell’s structural stability, cell motility, mechanosensing, chromosome organization, gene regulation, cell differentiation, DNA damage repair, and telomere protection. Mutations of the lamin A/C gene, incorrect processing of the protein, and lamin A/C deregulation can lead to various diseases and cancer. This review touches on diseases caused by mutation and incorrect processing of lamin A/C, called laminopathies. The effect of lamin A/C deregulation in cancer is also reviewed, and lamin A/C’s potential in helping to diagnose prostate cancers more accurately is discussed.

Abstract

This review is focused on lamin A/C, a nuclear protein with multiple functions in normal and diseased cells. Its functions, as known to date, are summarized. This summary includes its role in maintaining a cell’s structural stability, cell motility, mechanosensing, chromosome organization, gene regulation, cell differentiation, DNA damage repair, and telomere protection. As lamin A/C has a variety of critical roles within the cell, mutations of the lamin A/C gene and incorrect processing of the protein results in a wide variety of diseases, ranging from striated muscle disorders to accelerated aging diseases. These diseases, collectively termed laminopathies, are also touched upon. Finally, we review the existing evidence of lamin A/C’s deregulation in cancer. Lamin A/C deregulation leads to various traits, including genomic instability and increased tolerance to mechanical insult, which can lead to more aggressive cancer and poorer prognosis. As lamin A/C’s expression in specific cancers varies widely, currently known lamin A/C expression in various cancers is reviewed. Additionally, Lamin A/C’s potential as a biomarker in various cancers and as an aid in more accurately diagnosing intermediate Gleason score prostate cancers is also discussed.

Promotion of esophageal adenocarcinoma metastasis via Wnt/ß-catenin signal pathway by sorting nexins 3

BACKGROUND

Esophageal adenocarcinoma is often associated with late diagnoses, poor prognoses, significant morbidities, and high mortality rates. Aberrant expression of Wnt/β-catenin signal pathways were observed in the tumorigenesis and metastasis of esophageal adenocarcinoma. Sorting nexins 3 has been shown to participate in Wnt protein sorting and regulate Wnt/β-catenin signal transduction. Thus, we studied the role and molecular mechanism of sorting nexins 3 in esophageal adenocarcinoma.

METHODS

Tissue microassay were used to analyze the expression of sorting nexins 3 in esophageal adenocarcinoma tissue and its relationship with survival rate. Using in vivo and in vitro models, we further investigated the effect of sorting nexins 3 on tumor growth and metastasis and underling mechanism.

RESULTS

Immunohistochemical staining of human esophageal adenocarcinoma tissue microassay revealed an increased sorting nexins 3 level in esophageal adenocarcinoma tissue and high expression of sorting nexins 3 correlated with the poor prognosis. In vitro study showed that sorting nexins 3 knockdown suppressed esophageal adenocarcinoma cell invasion, metastasis, and epithelial-mesenchymal translation (EMT) process, and this result was confirmed by in vivo tumor metastasis assays. Moreover, we further proved that sorting nexins 3 affected cell invasion and EMT through Wnt/β-catenin signal pathway.

CONCLUSION

Our data provided strong evidence that sorting nexins 3 played a critical role in esophageal adenocarcinoma metastasis through Wnt/β-catenin signal pathway.

New insights into mechanisms of nuclear translocation of G-protein coupled receptors

The G-protein coupled receptor (GPCR) signaling was long believed to involve activation of receptor exclusively at the cell surface, followed by its binding to heterotrimeric G-proteins and arrestins to trigger various intracellular signaling cascades, and termination of signaling by internalization of the receptor. It is now accepted that many GPCRs continue to signal after internalization in the endosomes. Since the breakthrough discoveries of nuclear binding sites for their ligands in 1980s, several GPCRs have been detected at cell nuclei. But mechanisms of nuclear localization of GPCRs, many of whom contain putative nuclear localization signals, remain poorly understood to date. Nevertheless, it is known that subcellular trafficking of GPCRs is regulated by members of Ras superfamily of small GTPases, most notably by Rab and Arf GTPases. In this commentary, we highlight several recent studies which suggest novel roles of small GTPases, importins and sorting nexin proteins in the nuclear translocation of GPCRs via vesicular transport pathways. Taken together with increasing evidence for in vivo functionality of the nuclear GPCRs, better understanding of their trafficking will provide valuable clues in cell biology.