Cytoplasmic accumulation and plasma membrane association of anillin and Ect2 promote confined migration and invasion.

Cells migrating in confinement experience mechanical challenges whose consequences on cell migration machinery remain only partially understood. Here, we demonstrate that a pool of the cytokinesis regulatory protein anillin is retained during interphase in the cytoplasm of different cell types. Confinement induces recruitment of cytoplasmic anillin to plasma membrane at the poles of migrating cells, which is further enhanced upon nuclear envelope (NE) rupture(s). Rupture events also enable the cytoplasmic egress of predominantly nuclear RhoGEF Ect2. Anillin and Ect2 redistributions scale with microenvironmental stiffness and confinement, and are observed in confined cells in vitro and in invading tumor cells in vivo. Anillin, which binds actomyosin at the cell poles, and Ect2, which activates RhoA, cooperate additively to promote myosin II contractility, and promote efficient invasion and extravasation. Overall, our work provides a mechanistic understanding of how cytokinesis regulators mediate RhoA/ROCK/myosin II-dependent mechanoadaptation during confined migration and invasive cancer progression.

Photocatalytic Gold Recovery from Industrial Gold Plating Effluent by ZnO Nanoparticles: Optimum Condition and Possible Applications.

The comparative study of photocatalytic gold recovery from cyanide-based gold plating solution was explored via commercial and hydrothermally synthesized ZnO nanoparticles (NPs). The effects of hydrothermal temperatures on the properties and photocatalytic activities of synthesized ZnO NPs were investigated. In addition, the effects of operating parameters including types of hole scavenger, concentrations of the best hole scavenger, the initial pH of wastewater, and photocatalyst dosages were examined. The obtained results demonstrated that the commercial ZnO NPs exhibited a higher photocatalytic activity for gold recovery than that of the synthesized ones owing to their good crystal quality and the presence of non-lattice zinc ions and appropriate non-lattice oxygen ions. Via the commercial ZnO NPs, the gold ions were almost completely recovered from the cyanide-based gold plating effluent within 7 h at an initial pH of 11.0 in the presence of 10 vol % C2H5OH and 1.0 g/L of photocatalyst loading with a pseudo-first-order rate constant of 0.2637 h-1. Finally, the resultant gold-decorated ZnO NPs exhibited a higher photocatalytic property for color reduction from industrial wastewater and antibacterial activity than that of fresh ZnO NPs. The results obtained in this study possess benefits and pave the way for waste remediation and management for the plating industries.

Giant obscurin regulates migration and metastasis via RhoA-dependent cytoskeletal remodeling in pancreatic cancer.

Obscurins, encoded by the OBSCN gene, are giant cytoskeletal proteins with structural and regulatory roles. Large scale omics analyses reveal that OBSCN is highly mutated across different types of cancer, exhibiting a 5-8% mutation frequency in pancreatic cancer. Yet, the functional role of OBSCN in pancreatic cancer progression and metastasis has to be delineated. We herein show that giant obscurins are highly expressed in normal pancreatic tissues, but their levels are markedly reduced in pancreatic ductal adenocarcinomas. Silencing of giant obscurins in non-tumorigenic Human Pancreatic Ductal Epithelial (HPDE) cells and obscurin-expressing Panc5.04 pancreatic cancer cells induces an elongated, spindle-like morphology and faster cell migration via cytoskeletal remodeling. Specifically, depletion of giant obscurins downregulates RhoA activity, which in turn results in reduced focal adhesion density, increased microtubule growth rate and faster actin dynamics. Although OBSCN knockdown is not sufficient to induce de novo tumorigenesis, it potentiates tumor growth in a subcutaneous implantation model and exacerbates metastasis in a hemispleen murine model of pancreatic cancer metastasis, thereby shortening survival. Collectively, these findings reveal a critical role of giant obscurins as tumor suppressors in normal pancreatic epithelium whose loss of function induces RhoA-dependent cytoskeletal remodeling, and promotes cell migration, tumor growth and metastasis.

The fluid shear stress sensor TRPM7 regulates tumor cell intravasation.

Tumor cell intravasation preferentially occurs in regions of low fluid shear because high shear is detrimental to tumor cells. Here, we describe a molecular mechanism by which cells avoid high shear during intravasation. The transition from migration to intravasation was modeled using a microfluidic device where cells migrating inside longitudinal tissue-like microchannels encounter an orthogonal channel in which fluid flow induces physiological shear stresses. This approach was complemented with intravital microscopy, patch-clamp, and signal transduction imaging techniques. Fluid shear-induced activation of the transient receptor potential melastatin 7 (TRPM7) channel promotes extracellular calcium influx, which then activates RhoA/myosin-II and calmodulin/IQGAP1/Cdc42 pathways to coordinate reversal of migration direction, thereby avoiding shear stress. Cells displaying higher shear sensitivity due to higher TRPM7 activity levels intravasate less efficiently and establish less invasive metastatic lesions. This study provides a mechanistic interpretation for the role of shear stress and its sensor, TRPM7, in tumor cell intravasation.

Dorsoventral polarity directs cell responses to migration track geometries.

How migrating cells differentially adapt and respond to extracellular track geometries remains unknown. Using intravital imaging, we demonstrate that invading cells exhibit dorsoventral (top-to-bottom) polarity in vivo. To investigate the impact of dorsoventral polarity on cell locomotion through different confining geometries, we fabricated microchannels of fixed cross-sectional area, albeit with distinct aspect ratios. Vertical confinement, exerted along the dorsoventral polarity axis, induces myosin II-dependent nuclear stiffening, which results in RhoA hyperactivation at the cell poles and slow bleb-based migration. In lateral confinement, directed perpendicularly to the dorsoventral polarity axis, the absence of perinuclear myosin II fails to increase nuclear stiffness. Hence, cells maintain basal RhoA activity and display faster mesenchymal migration. In summary, by integrating microfabrication, imaging techniques, and intravital microscopy, we demonstrate that dorsoventral polarity, observed in vivo and in vitro, directs cell responses in confinement by spatially tuning RhoA activity, which controls bleb-based versus mesenchymal migration.

Confinement hinders motility by inducing RhoA-mediated nuclear influx, volume expansion, and blebbing.

Cells migrate in vivo through complex confining microenvironments, which induce significant nuclear deformation that may lead to nuclear blebbing and nuclear envelope rupture. While actomyosin contractility has been implicated in regulating nuclear envelope integrity, the exact mechanism remains unknown. Here, we argue that confinement-induced activation of RhoA/myosin-II contractility, coupled with LINC complex-dependent nuclear anchoring at the cell posterior, locally increases cytoplasmic pressure and promotes passive influx of cytoplasmic constituents into the nucleus without altering nuclear efflux. Elevated nuclear influx is accompanied by nuclear volume expansion, blebbing, and rupture, ultimately resulting in reduced cell motility. Moreover, inhibition of nuclear efflux is sufficient to increase nuclear volume and blebbing on two-dimensional surfaces, and acts synergistically with RhoA/myosin-II contractility to further augment blebbing in confinement. Cumulatively, confinement regulates nuclear size, nuclear integrity, and cell motility by perturbing nuclear flux homeostasis via a RhoA-dependent pathway.

A Direct Podocalyxin-Dynamin-2 Interaction Regulates Cytoskeletal Dynamics to Promote Migration and Metastasis in Pancreatic Cancer Cells.

The sialoglycoprotein podocalyxin is absent in normal pancreas but is overexpressed in pancreatic cancer and is associated with poor clinical outcome. Here, we investigate the role of podocalyxin in migration and metastasis of pancreatic adenocarcinomas using SW1990 and Pa03c as cell models. Although ezrin is regarded as a cytoplasmic binding partner of podocalyxin that regulates actin polymerization via Rac1 or RhoA, we did not detect podocalyxin-ezrin association in pancreatic cancer cells. Moreover, depletion of podocalyxin did not alter actin dynamics or modulate Rac1 and RhoA activities in pancreatic cancer cells. Using mass spectrometry, bioinformatics analysis, coimmunoprecipitation, and pull-down assays, we discovered a novel, direct binding interaction between the cytoplasmic tail of podocalyxin and the large GTPase dynamin-2 at its GTPase, middle, and pleckstrin homology domains. This podocalyxin-dynamin-2 interaction regulated microtubule growth rate, which in turn modulated focal adhesion dynamics and ultimately promoted efficient pancreatic cancer cell migration via microtubule- and Src-dependent pathways. Depletion of podocalyxin in a hemispleen mouse model of pancreatic cancer diminished liver metastasis without altering primary tumor size. Collectively, these findings reveal a novel mechanism by which podocalyxin facilitates pancreatic cancer cell migration and metastasis. SIGNIFICANCE: These findings reveal that a novel interaction between podocalyxin and dynamin-2 promotes migration and metastasis of pancreatic cancer cells by regulating microtubule and focal adhesion dynamics.