Dual role of GRHL3 in bladder carcinogenesis depending on histological subtypes

The effect of grainyhead-like transcription factor 3 (GRHL3) on cancer development depends on the cancer subtypes as shown in tumor entities such as colorectal or oral squamous cell carcinomas. Here, we analyzed the subtype-specific role of GRHL3 in bladder carcinogenesis, comparing common urothelial carcinoma (UC) with squamous bladder cancer (sq-BLCA). We examined GRHL3 mRNA and protein expression in cohorts of patient samples, its prognostic role and its functional impact on tumorigeneses in different molecular and histopathological subtypes of bladder cancer. We showed for GRHL3 a reverse expression in squamous and urothelial bladder cancer subtypes. Stably GRHL3-overexpressing EJ28, J82, and SCaBER in vitro models revealed a tumor-suppressive function in squamous and an oncogenic role in the urothelial cancer cells affecting cell and colony growth, and migratory and invasive capacities. Transcriptomic profiling demonstrated highly subtype-specific GRHL3-regulated expression networks coined by the enrichment of genes involved in integrin-mediated pathways. In SCaBER, loss of ras homolog family member A (RHOA) GTPase activity was demonstrated to be associated with co-regulation of eukaryotic translation initiation factor 4E family member 3 (EIF4E3), a potential tumor suppressor gene. Thus, our data provide for the first time a detailed insight into the role of the transcription factor GRHL3 in different histopathological subtypes of bladder cancer.

RHO of plant signaling was established early in streptophyte evolution

The algal ancestors of land plants underwent a transition from a unicellular to a multicellular body plan.1 This transition likely took place early in streptophyte evolution, sometime after the divergence of the Chlorokybophyceae/Mesostigmatophyceae lineage, but before the divergence of the Klebsormidiophyceae lineage.2 How this transition was brought about is unknown; however, it was likely facilitated by the evolution of novel mechanisms to spatially regulate morphogenesis. In land plants, RHO of plant (ROP) signaling plays a conserved role in regulating polarized cell growth and cell division orientation to orchestrate morphogenesis.3,4,5,6,7,8 ROP constitutes a plant-specific subfamily of the RHO GTPases, which are more widely conserved throughout eukaryotes.9,10 Although the RHO family originated in early eukaryotes,11,12 how and when the ROP subfamily originated had remained elusive. Here, we demonstrate that ROP signaling was established early in the streptophyte lineage, sometime after the divergence of the Chlorokybophyceae/Mesostigmatophyceae lineage, but before the divergence of the Klebsormidiophyceae lineage. This period corresponds to when the unicellular-to-multicellular transition likely took place in the streptophytes. In addition to being critical for the complex morphogenesis of extant land plants, we speculate that ROP signaling contributed to morphological evolution in early streptophytes.

RHO GTPase of plants regulates polarized cell growth and cell division orientation during morphogenesis

Cell polarity-broadly defined as the asymmetric distribution of cellular activities and subcellular components within a cell-determines the geometry of cell growth and division during development. RHO GTPase proteins regulate the establishment of cell polarity and are conserved among eukaryotes. RHO of plant (ROP) proteins are a subgroup of RHO GTPases that are required for cellular morphogenesis in plants. However, how ROP proteins modulate the geometry of cell growth and division during the morphogenesis of plant tissues and organs is not well understood. To investigate how ROP proteins function during tissue development and organogenesis, we characterized the function of the single-copy ROP gene of the liverwort Marchantia polymorpha (MpROP). M. polymorpha develops morphologically complex three-dimensional tissues and organs exemplified by air chambers and gemmae, respectively. Mprop loss-of-function mutants form defective air chambers and gemmae, indicating ROP function is required for tissue development and organogenesis. During air chamber and gemma development in wild type, the MpROP protein is enriched to sites of polarized growth at the cell surface and accumulates at the expanding cell plate of dividing cells. Consistent with these observations, polarized cell growth is lost and cell divisions are misoriented in Mprop mutants. We propose that ROP regulates both polarized cell growth and cell division orientation in a coordinated manner to orchestrate tissue development and organogenesis in land plants.

MICAL1 activation by PAK1 mediates actin filament disassembly

The MICAL1 monooxygenase is an important regulator of filamentous actin (F-actin) structures. Although MICAL1 has been shown to be regulated via protein-protein interactions at the autoinhibitory carboxyl terminus, a link between actin-regulatory RHO GTPase signaling pathways and MICAL1 has not been established. We show that the CDC42 GTPase effector PAK1 associates with and phosphorylates MICAL1 on two serine residues, leading to accelerated F-actin disassembly. PAK1 binds to the amino-terminal catalytic monooxygenase and calponin homology domains, distinct from the autoinhibitory carboxyl terminus. Extracellular ligand stimulation leads to PAK-dependent phosphorylation, linking external signals to MICAL1 phosphorylation. Mass spectrometry indicates that MICAL1 co-expression with CDC42 and PAK1 increases MICAL1 association with hundreds of proteins, including the previously described MICAL1-interacting proteins RAB10 and RAB7A. These results provide insights into a redox-mediated pathway linking extracellular signals to cytoskeleton regulation via a RHO GTPase and indicate a means of communication between RHO and RAB GTPases.

Role of RHO family interacting cell polarization regulators (RIPORs) in health and disease: Recent advances and prospects

The RHO GTPase family has been suggested to play critical roles in cell growth, migration, and polarization. Regulators and effectors of RHO GTPases have been extensively explored in recent years. However, little attention has been given to RHO family interacting cell polarization regulators (RIPORs), a recently discovered protein family of RHO regulators. RIPOR proteins, namely, RIPOR1-3, bind directly to RHO proteins (A, B and C) via a RHO-binding motif and exert suppressive effects on RHO activity, thereby negatively influencing RHO-regulated cellular functions. In addition, RIPORs are phosphorylated by upstream protein kinases under chemokine stimulation, and this phosphorylation affects not only their subcellular localization but also their interaction with RHO proteins, altering the activation of RHO downstream targets and ultimately impacting cell polarity and migration. In this review, we provide an overview of recent studies on the function of RIPOR proteins in regulating RHO-dependent directional movement in immune responses and other pathophysiological functions.

B3GNT3 acts as a carcinogenic factor in endometrial cancer via facilitating cell growth, invasion and migration through regulating RhoA/RAC1 pathway-associated markers

BACKGROUND

Aberrant expression of beta-1,3-N-acetylglucosaminyltransferase-3 (B3GNT3) has been frequently clarified in various cancers, however, its role in endometrial cancer (EC) has not been assessed in detail.

PURPOSE

This study aimed to investigate the biological role of B3GNT3 in EC and simply explored the detailed mechanism.

METHODS

The EC RNA-Seq dataset from TCGA database was applied to evaluate the expression of B3GNT3 and assess its role on prognostic value. HEC-1-A and KLE cell lines of EC were used to perform loss- and gain-of-function B3GNT3 assays respectively. Quantitative real-time PCR (qRT-PCR) and western blot were used to measure the mRNA and protein levels of indicated molecules respectively. Cell counting kit-8, clone formation tests, and Transwell assay served to determine the changes of proliferative, invasive and migratory abilities of EC cells after altering the expression of B3GNT3.

RESULTS

B3GNT3 was found to be highly expressed in EC tissues compared to normal tissues according to the online public databases, which confirmed by the following qRT-PCR in 3 EC cell lines. Besides, high B3GNT3 expression presented a worse overall survival in EC patients as compared with low B3GNT3 expression group. Furthermore, functional experiments in vitro indicated that B3GNT3 could facilitate the cell growth, invasion and migration. Moreover, we found that downregulation of B3GNT3 significantly reduced the expression level of GTP-RhoA and GTP-RAC1, whereas upregulation of B3GNT3 presented the opposite results.

CONCLUSION

The results of current study demonstrate that B3GNT3 acts as an oncogene that promotes EC cells growth, invasion and migration possibly through regulating the RhoA/RAC1 signaling pathway-related markers, suggesting that B3GNT3 may be a candidate biomarker for EC therapeutic intervention.

ARF6 controls RHOB targeting to endosomes regulating cancer cell invasion

Endocytic trafficking has emerged as an essential mechanism to spatiotemporally coordinate signaling protein complexes that control cytoskeletal dynamics and cell motility. Our study established an unexpected regulatory mechanism whereby ADP ribosylation factors 6 (ARF6) controls the stability and endosomal localization of RAS homologous protein B (RHOB) to regulate cell invasion downstream of the oncogenic receptor tyrosine kinase, MET.