α-Parvin Defines a Specific Integrin Adhesome to Maintain the Glomerular Filtration Barrier

BACKGROUND

The cell-matrix adhesion between podocytes and the glomerular basement membrane is essential for the integrity of the kidney's filtration barrier. Despite increasing knowledge about the complexity of integrin adhesion complexes, an understanding of the regulation of these protein complexes in glomerular disease remains elusive.

METHODS

We mapped the in vivo composition of the podocyte integrin adhesome. In addition, we analyzed conditional knockout mice targeting a gene (Parva) that encodes an actin-binding protein (α-parvin), and murine disease models. To evaluate podocytes in vivo, we used super-resolution microscopy, electron microscopy, multiplex immunofluorescence microscopy, and RNA sequencing. We performed functional analysis of CRISPR/Cas9-generated PARVA single knockout podocytes and PARVA and PARVB double knockout podocytes in three- and two-dimensional cultures using specific extracellular matrix ligands and micropatterns.

RESULTS

We found that PARVA is essential to prevent podocyte foot process effacement, detachment from the glomerular basement membrane, and the development of FSGS. Through the use of in vitro and in vivo models, we identified an inherent PARVB-dependent compensatory module at podocyte integrin adhesion complexes, sustaining efficient mechanical linkage at the filtration barrier. Sequential genetic deletion of PARVA and PARVB induces a switch in structure and composition of integrin adhesion complexes. This redistribution of these complexes translates into a loss of the ventral actin cytoskeleton, decreased adhesion capacity, impaired mechanical resistance, and dysfunctional extracellular matrix assembly.

CONCLUSIONS

The findings reveal adaptive mechanisms of podocyte integrin adhesion complexes, providing a conceptual framework for therapeutic strategies to prevent podocyte detachment in glomerular disease.

The focal adhesion protein Integrin-Linked Kinase (ILK) as an important player in breast cancer pathogenesis

Cell-extracellular matrix interactions, or focal adhesions (FA), are crucial for tissue homeostasis but are also implicated in cancer. Integrin-Linked Kinase (ILK) is an abundantly expressed FA protein involved in multiple signaling pathways. Here, we reviewed the current literature on the role of ILK in breast cancer (BC). Articles included in vitro and in vivo experiments as well as studies in human BC samples. ILK attenuation via silencing or pharmaceutical inhibition, leads to apoptosis or inhibition of epithelial-to-mesenchymal transition, and cell invasion whereas ILK overexpression suppresses anoikis and promotes tumor growth and metastasis. Finally, ILK is upregulated in BC tumors and its expression is associated with grade, and metastasis. Therefore, ILK should be evaluated as a potential anti-cancer pharmaceutical target.

Circular RNA circCLK3 promotes the progression of tongue squamous cell carcinoma via miR-455-5p/PARVA axis

A previous study has elucidated that circular RNA circCLK3 acts as an oncogenic gene in cervical cancer. However, the role and regulatory mechanism of circCLK3 in tongue squamous cell carcinoma (TSCC) remain unknown. Quantitative real-time PCR was used to examine targeted gene expression in different groups. Cell viability and proliferation were investigated by MTT and 5-ethynyl-2'-deoxyuridine assays. Cell migration and invasion were detected by Transwell assays, and cell apoptosis was measured by flow cytometry analysis. The interaction among genes was investigated using luciferase reporter assay, RNA pull-down assay, and RNA immunoprecipitation assay. In the present study, our findings revealed the upregulated expression of circCLK3 in TSCC tissues and cell lines. CircCLK3 knockdown suppressed cell proliferation, migration invasion, and induced cell cycle arrest at G0/G1 phase in TSCC. Moreover, circCLK3 acted as a molecular sponge for miR-455-5p. PARVA was the target gene of miR-455-5p. Furthermore, the negative correlation between expression of miR-455-5p and circCLK3 or PARVA in TSCC tissues was discovered. Rescue assays indicated that PARVA overexpression reversed the circCLK3 knockdown-mediated inhibitory effects on the progression of TSCC. In summary, circCLK3 exerts its carcinogenic effects on TSCC progression via absorbing miR-455-5p to upregulate PARVA, which expands our knowledge on the underlying mechanism of TSCC.

Downregulation of PARVA promotes metastasis by modulating integrin-linked kinase activity and regulating MAPK/ERK and MLC2 signaling in prostate cancer

Background

Metastasis is the predominant cause of mortality in prostate cancer (PCa); however, the underlying mechanisms are largely uncharted. Here, we found that Parvin alpha (PARVA) is downregulated in PCa and its loss is associated with clinical metastasis. We further explored the mechanistic basis of this finding.

Methods

The mRNA expression of PARVA was identified by analysis of the Gene Expression Omnibus (GEO) and The Cancer Genome Atlas (TCGA) data sets. Immunohistochemistry (IHC) analysis was performed to evaluate the PARVA expression pattern in 198 PCa tissues, and 36 metastatic lymph node tissues. The function and molecular mechanism by which PARVA affects PCa were investigated in vitro using knockdown and overexpression cell lines. The effect of PARVA in cell proliferation, migration, and invasion in PCa cells was detected by MTS assay and Transwell assay. Real-time polymerase chain reaction (PCR) and Western blot analysis were used to assess the gene expression in mRNA and protein level.

Results

The microarray data analysis indicated that PARVA was drastically downregulated in primary and metastatic PCa compared with normal and primary samples, respectively (all P<0.001). Multivariate Cox regression analysis suggested that downregulation of PARVA in PCa was an independent prognostic factor for poor biochemical recurrence (BCR)-free survival (P<0.01). IHC analysis confirmed that PARVA was frequently downregulated in metastatic and primary PCa tissues (All P<0.001). Furthermore, PARVA expression was found to be associated with Gleason score, pathological stage, extracapsular extension, and lymph node invasion (All P<0.05). Knockdown of PARVA triggered cell migration and invasion in vitro, whereas overexpression of PARVA reverted the invasive phenotypes. Mechanistic investigations identified that overexpression of PARVA repressed the mitogen-activated protein kinase (MAPK)/extracellular signal-regulated kinase (ERK) phosphorylation via inhibiting the integrin-linked kinase (ILK) biological function. With knockdown of ILK, the downregulated MAPK/ERK phosphorylation and Myosin Light Chain 2 (MLC2) expression by PARVA overexpression were abolished, indicating that the PARVA effect on PCa is ILK/MAPK/ERK pathway dependent.

Conclusions

Our study revealed that loss of PARVA expression in PCa promotes metastasis by releasing the inhibition of ILK activity, followed by the activation of MAPK/ERK and MLC2 signaling.

Silencing of Growth Differentiation Factor-15 Promotes Breast Cancer Cell Invasion by Down-regulating Focal Adhesion Genes

BACKGROUND/AIM

As metastasis accounts for most breast cancer (BC)-related deaths, identifying key players becomes research priority. Growth differentiation factor-15 (GDF15), a member of the transforming growth factor-β superfamily, is affected by the actin cytoskeleton and has been associated with cancer. However, its exact role in BC cell invasiveness is vague.

MATERIALS AND METHODS

GDF15 short-hairpin (shRNA)-mediated silencing was used to inhibit GDF15 expression in MCF-7 and MDA-MB-231 BC cells and gene expression of relevant focal adhesion (FA) genes, cell migration, invasion and tumor spheroid invasion were subsequently analyzed.

RESULTS

GDF15 silencing promoted cell migration, cell invasion as well as tumor spheroid invasion and up-regulated urokinase plasminogen activator (uPA) and FA genes, integrin-linked kinase (ILK), LIM zinc finger domain containing 1 (LIMS1), α-parvin (PARVA), and RAS suppressor-1 (RSU1). Computational analysis of Cancer Genome Atlas BC dataset however, revealed no significant correlation between GDF15 expression and metastasis pointing towards a more complex molecular interplay between GDF15, actin cytoskeleton and FA-related genes which ultimately affects their expression pattern, in vivo.

CONCLUSION

GDF15 suppresses BC cell invasion in vitro through down-regulation of FA genes but its role in BC is more complicated in vivo and warrants further investigation.

Inhibition of Breast Cancer Cell Invasion by Ras Suppressor-1 (RSU-1) Silencing Is Reversed by Growth Differentiation Factor-15 (GDF-15)

Extracellular matrix (ECM)-related adhesion proteins are important in metastasis. Ras suppressor-1 (RSU-1), a suppressor of Ras-transformation, is localized to cell–ECM adhesions where it interacts with the Particularly Interesting New Cysteine-Histidine rich protein (PINCH-1), being connected to Integrin Linked Kinase (ILK) and alpha-parvin (PARVA), a direct actin-binding protein. RSU-1 was also found upregulated in metastatic breast cancer (BC) samples and was recently demonstrated to have metastasis-promoting properties. In the present study, we transiently silenced RSU-1 in BC cells, MCF-7 and MDA-MB-231. We found that RSU-1 silencing leads to downregulation of Growth Differentiation Factor-15 (GDF-15), which has been associated with both actin cytoskeleton reorganization and metastasis. RSU-1 silencing also reduced the mRNA expression of PINCH-1 and cell division control protein-42 (Cdc42), while increasing that of ILK and Rac regardless of the presence of GDF-15. However, the downregulation of actin-modulating genes PARVA, RhoA, Rho associated kinase-1 (ROCK-1), and Fascin-1 following RSU-1 depletion was completely reversed by GDF-15 treatment in both cell lines. Moreover, complete rescue of the inhibitory effect of RSU-1 silencing on cell invasion was achieved by GDF-15 treatment, which also correlated with matrix metalloproteinase-2 expression. Finally, using a graph clustering approach, we corroborated our findings. This is the first study providing evidence of a functional association between RSU-1 and GDF-15 with regard to cancer cell invasion.