PDf file - 1.2MB, CA IX co-localization with NBC1 in A549 cells is presented in the form of Z-stack corresponding to Figure 6B.

PDf file - 903K, Immunohistochemical analysis of the parallel expression of CA IX and PKA substrates.

PDf file - 71K, List of primers used for cloning of phosphorylation mutants and CA IX-CA II and CA IX-CA XII chimeras. Boldcase sequences represent nucleotides aligning to CA IX part.

PDf file - 1.3MB, CA IX co-localization with PKA-phosphorylated substrates in A549 cells is presented in the form of Z-stack corresponding to Figure 6A.

The choroid plexus secrets cerebrospinal fluid (CSF) composed of electrolytes, cytokines, growth factors, metabolites and extracellular vesicles (EVs) that flow through the interconnected brain ventricles. On their course, CSF components can act as signals that affect, for example, neural stem cells (NSCs) residing in niches of the ventricular wall. We studied EV-born CSF signals in an in vitro culture system. We purified EVs from the secretome of a choroid plexus cell line (Z310 cells), and from primary choroid plexus cultures and co-cultured those EVs with NSCs isolated from the niche of the lateral and the third ventricle. EVs(Z310) and EVs(CHP) were purified by differential centrifugation. This yielded fractions of EVs of 50-150-nm diameter that induced a complex multicellular network formation and NSC differentiation. Both types of EV converted the round NSCs to cells that extended long processes that contacted nearby, alike-shaped cells. Mass spectrometry showed that the differentiation-inducing EVZ310 were enriched for membrane and membrane-associated proteins involved in cell differentiation, membrane trafficking, and membrane organization. We hypothesize that this type of EV (Z310) cargo causes changes of stem cell morphology that leads to multicellular networks in the niches. This cell-shape transition may represent an initial step in NSC differentiation.

Intermediate progenitor cells (IPCs) are neocortical neuronal precursors. Although IPCs play crucial roles in corticogenesis, their molecular features remain largely unknown. In this study, we aimed to characterize the molecular profile of IPCs. We isolated TBR2-positive (+) IPCs and TBR2-negative (-) cell populations in the developing mouse cortex. Comparative genome-wide gene expression analysis of TBR2+ IPCs versus TBR2- cells revealed differences in key factors involved in chromatid segregation, cell-cycle regulation, transcriptional regulation, and cell signaling. Notably, mutation of many IPC genes in human has led to intellectual disability and caused a wide range of cortical malformations, including microcephaly and agenesis of corpus callosum. Loss-of-function experiments in cortex-specific mutants of Esco2, one of the novel IPC genes, demonstrate its critical role in IPC maintenance, and substantiate the identification of a central genetic determinant of IPC biogenesis. Our data provide novel molecular characteristics of IPCs in the developing mouse cortex.

A rodent-transmitted enveloped lymphocytic choriomeningitis virus (LCMV) is an RNA virus causing persistent infection. During persistent infection, a unique strain MX of LCMV does not yield infectious virions, therefore it is not able to use a receptor for its dissemination, and spreads by cell-to-cell contacts. Virus can be transported to the neighboring cell by different cellular structures such as tunneling nanotubes or cytonemes. Using q-PCR, immunofluorescence, siRNA and western blot, we show that keratin 1 (K1) is essential for the persistent infection caused by LCMV strain MX, and its absence very effectively slows down the course of infection. In contrast, other LCMV strains, namely Clone 13 and Armstrong, which produce expression of K1, desmosomes in cells expressing K1 (42-MG-BA) but not in cells without K1 expression (NIH/3T3). We conclude that the presence of the virus enhances the K1 expression, while the presence of K1 protein potentiates the viral spread in persistently infected cells. Keywords: lymphocytic choriomeningitis virus; keratin 1; persistent infection; desmosomes; virus transport.

BACKGROUND:Carbonic anhydrase IX (CA IX) is a transmembrane enzyme that is present in many types of solid tumors. Expression of CA IX is driven predominantly by the hypoxia-inducible factor (HIF) pathway and helps to maintain intracellular pH homeostasis under hypoxic conditions, resulting in acidification of the tumor microenvironment. Carnosine (β-alanyl-L-histidine) is an anti-tumorigenic agent that inhibits the proliferation of cancer cells. In this study, we investigated the role of CA IX in carnosine-mediated antitumor activity and whether the underlying mechanism involves transcriptional and translational modulation of HIF-1α and CA IX and/or altered CA IX function.METHODS:The effect of carnosine was studied using two-dimensional cell monolayers of several cell lines with endogenous CA IX expression as well as Madin Darby canine kidney transfectants, three-dimensional HeLa spheroids, and an in vivo model of HeLa xenografts in nude mice. mRNA and protein expression and protein localization were analyzed by real-time PCR, western blot analysis, and immunofluorescence staining, respectively. Cell viability was measured by a flow cytometric assay. Expression of HIF-1α and CA IX in tumors was assessed by immunohistochemical staining. Real-time measurement of pH was performed using a sensor dish reader. Binding of CA IX to specific antibodies and metabolon partners was investigated by competitive ELISA and proximity ligation assays, respectively.RESULTS:Carnosine increased the expression levels of HIF-1α and HIF targets and increased the extracellular pH, suggesting an inhibitory effect on CA IX-mediated acidosis. Moreover, carnosine significantly inhibited the growth of three-dimensional spheroids and tumor xenografts compared with untreated controls. Competitive ELISA showed that carnosine disrupted binding between CA IX and antibodies specific for its catalytic domain. This finding was supported by reduced formation of the functional metabolon of CA IX and anion exchanger 2 in the presence of carnosine.CONCLUSIONS:Our results indicate that interaction of carnosine with CA IX leads to conformational changes of CA IX and impaired formation of its metabolon, which in turn disrupts CA IX function. These findings suggest that carnosine could be a promising anticancer drug through its ability to attenuate the activity of CA IX.

G250 (Girentuximab) is a chimeric IgG1 monoclonal antibody (MAb) currently being evaluated as an immunotherapy for kidney cancer. It targets carbonic anhydrase protein (CA Ⅸ), a transmembrane carbonic anhydrase (CA) isoform, which is regulated by VHL/HIF pathway and hence expressed in the majority of renal cell carcinomas (RCCs) as well as in hypoxic non‑RCC tumours. CA Ⅸ functions in pH regulation and cell migration/invasion, and supports tumour cell survival in hypoxia and/or acidosis. It contains a highly active extracellular catalytic domain (CA) extended N-terminally with a proteoglycan-like region and C-terminally with short transmembrane and intracellular regions. Here we characterize the binding and internalization properties of G250, as well as its therapeutic effects in animal model, and discuss the impact of G250‑mediated immunotherapy in non‑RCC tumours. We demonstrated that G250 MAb recognizes a conformational epitope in the CA domain, detects the soluble CA Ⅸ ectodomain (ECD), but not the splicing variant, and does not cross-react with CA Ⅰ, Ⅱ, and Ⅻ isoforms. We showed that G250 internalizes via clathrin-coated vesicles, escapes degradation in lysosomes and enters the recycling pathway via the perinuclear compartment. This results in long intracellular persistence and enables consecutive internalization cycles. Moreover, the recycled antibody maintains an intact Fc portion potentially capable of continuous induction of antibody-dependent cell-mediated cytotoxicity (ADCC) response, thus explaining its therapeutic efficacy. Finally, we showed that G250 treatment is effective against HT-29 colorectal carcinoma xenografts that differ from RCC by more heterogeneous, hypoxia-related expression of CA Ⅸ. These results suggest potential therapeutic usefulness of the G250 MAb in non-RCC tumours.

g250 (girentuximab) is a chimeric igg1 monoclonal antibody (Mab) currently being evaluated as an immunotherapy for kidney cancer. it targets carbonic anhydrase protein (CA IX), a transmembrane carbonic anhydrase (ca) isoform, which is regulated by VHl/Hif pathway and hence expressed in the majority of renal cell carcinomas (rccs) as well as in hypoxic non-rcc tumours. CA IX functions in pH regulation and cell migration/invasion, and supports tumour cell survival in hypoxia and/or acidosis. it contains a highly active extracellular catalytic domain (ca) extended n-terminally with a proteoglycan-like region and c-terminally with short transmembrane and intracellular regions. Here we characterize the binding and internalization properties of g250, as well as its therapeutic effects in animal model, and discuss the impact of g250-mediated immunotherapy in non-rcc tumours. We demonstrated that g250 Mab recognizes a conformational epitope in the ca domain, detects the soluble CA IX ectodomain (ECD), but not the splicing variant, and does not cross‐react with CA I, II, and XII isoforms. We showed that G250 internalizes via clathrin-coated vesicles, escapes degradation in lysosomes and enters the recycling pathway via the perinuclear compartment. this results in long intracellular persistence and enables consecutive internalization cycles. Moreover, the recycled antibody maintains an intact fc portion potentially capable of continuous induction of antibody-dependent cell-mediated cytotoxicity (ADCC) response, thus explaining its therapeutic efficacy. Finally, we showed that G250 treatment is effective against Ht-29 colorectal carcinoma xenografts that differ from rcc by more heterogeneous, hypoxia-related expression of CA IX. These results suggest potential therapeutic usefulness of the g250 Mab in non-rcc tumours.

Multidrug resistance (MDR) is a phenomenon in which cells become resistant to cytostatic drugs and other substances with diverse chemical structures and cytotoxicity mechanisms. The most often observed molecular mechanism for MDR includes high levels of P-glycoprotein (P-gp) - an ABCB1 member of the ABC drug transporter family. Overexpression of P-gp in neoplastic tissue is an obstacle to chemotherapeutic treatment. Herein, we were focused on differences in apoptosis induced by cisplatin (no substrate for P-gp) between P-gp-positive and P-gp-negative L1210 cells. P-gp-positive cells were obtained by either L1210 cell adaptation to vincristine (R) or L1210 cell transfection with the human gene for P-gp (T) and compared with parental L1210 cells (S). R and T cells were more resistant to CisPt than S cells. R and T cell resistance to CisPt-induced apoptosis could not be reversed by verapamil (a well-known P-gp inhibitor), which excludes P-gp transport activity as a cause of CisPt resistance. CisPt induced a more pronounced entry into apoptosis in S than R and T cells, which was measured using the annexin-V/propidium iodide apoptosis kit. CisPt induced more pronounced caspase-3 activation in S than R and T cells. CisPt did not induce changes in the P-gp protein level for R and T cells. While similar levels of Bax and Bcl-2 proteins were observed in P-gp-negative and P-gp-positive cells, CisPt induced a more significant decrease in Bcl-2 levels for S cells than P-gp-positive cells. Expression of p53 and its molecular chaperone Hsp90 were more pronounced in R and T than S cells. Moreover, CisPt enhanced the upregulation of p53 and Hsp90 in R and T cells to a higher degree than S cells. Apoptosis was shown to be the prevalent mode of cell death in S, R and T cells by the typical DNA fragmentation and cell ultrastructure changes. All of the above findings indicate that P-gp, independent of its drug efflux activity, induced changes in cell regulatory pathways that confer a partial loss of cisplatin sensitivity. (C) 2012 Elsevier Ltd. All rights reserved.

In the hypoxic regions of a tumor, carbonic anhydrase IX (CA IX) is an important transmembrane component of the pH regulatory machinery that participates in bicarbonate transport. Because tumor pH has implications for growth, invasion, and therapy, determining the basis for the contributions of CA IX to the hypoxic tumor microenvironment could lead to new fundamental and practical insights. Here, we report that Thr443 phosphorylation at the intracellular domain of CA IX by protein kinase A (PKA) is critical for its activation in hypoxic cells, with the fullest activity of CA IX also requiring dephosphorylation of Ser448. PKA is activated by cAMP, which is elevated by hypoxia, and we found that attenuating PKA in cells disrupted CA IX-mediated extracellular acidification. Moreover, following hypoxia induction, CA IX colocalized with the sodium-bicarbonate cotransporter and other PKA substrates in the leading edge membranes of migrating tumor cells, in support of the concept that bicarbonate metabolism is spatially regulated at cell surface sites with high local ion transport and pH control. Using chimeric CA IX proteins containing heterologous catalytic domains derived from related CA enzymes, we showed that CA IX activity was modulated chiefly by the intracellular domain where Thr443 is located. Our findings indicate that CA IX is a pivotal mediator of the hypoxia-cAMP–PKA axis, which regulates pH in the hypoxic tumor microenvironment. Cancer Res; 71(24); 7558–67. 2011 AACR.

Abstract In the hypoxic regions of a tumor, carbonic anhydrase IX (CA IX) is an important transmembrane component of the pH regulatory machinery that participates in bicarbonate transport. Because tumor pH has implications for growth, invasion, and therapy, determining the basis for the contributions of CA IX to the hypoxic tumor microenvironment could lead to new fundamental and practical insights. Here, we report that Thr443 phosphorylation at the intracellular domain of CA IX by protein kinase A (PKA) is critical for its activation in hypoxic cells, with the fullest activity of CA IX also requiring dephosphorylation of Ser448. PKA is activated by cAMP, which is elevated by hypoxia, and we found that attenuating PKA in cells disrupted CA IX-mediated extracellular acidification. Moreover, following hypoxia induction, CA IX colocalized with the sodium-bicarbonate cotransporter and other PKA substrates in the leading edge membranes of migrating tumor cells, in support of the concept that bicarbonate metabolism is spatially regulated at cell surface sites with high local ion transport and pH control. Using chimeric CA IX proteins containing heterologous catalytic domains derived from related CA enzymes, we showed that CA IX activity was modulated chiefly by the intracellular domain where Thr443 is located. Our findings indicate that CA IX is a pivotal mediator of the hypoxia-cAMP–PKA axis, which regulates pH in the hypoxic tumor microenvironment. Cancer Res; 71(24); 7558–67. ©2011 AACR.

Carbonic anhydrase IX (CA IX) is a suitable target for various anticancer strategies. It is a cell surface protein that is present in human tumors, but not in the corresponding normal tissues. Expression of CA IX is induced by hypoxia and correlates with cancer prognosis in many tumor types. Moreover, CA IX is functionally implicated in cancer progression as a pro-survival factor protecting cancer cells against hypoxia and acidosis via its capability to regulate pH and cell adhesion. Cancer-related distribution of CA IX allows for targeting cancer cells by antibodies binding to its extracellular domain, whereas functional involvement of CA IX opens the possibility to hit cancer cells by blocking their adaptation to physiologic stresses via inhibition of CA IX enzyme activity. The latter strategy is recently receiving considerable attention and great efforts are made to produce CA IX-selective inhibitor derivatives with anticancer effects. On the other hand, targeting CA IX-expressing cells by immunotherapy has reached clinical trials and is close to application in treatment of renal cell carcinoma patients. Nevertheless, development and characterization of new CA IX-specific antibodies is still ongoing. Here we describe a mouse monoclonal antibody VII/20 directed to catalytic domain of CA IX. We show that upon binding to CA IX, the VII/20 MAb undergoes efficient receptor-mediated internalization, which is a process regulating abundance and signaling of cell surface proteins and has considerable impact on immunotherapy. We evaluated biological properties of the MAb and demonstrated its capacity to elicit anti-cancer effect in mouse xenograft model of colorectal carcinoma. Thus, the VII/20 MAb might serve as a tool for preclinical studies of immunotherapeutic strategies against non-RCC tumors. These have not been explored so far and include broad spectrum of cancer types, treatment of which might benefit from CA IX-mediated targeting.

Overexpression of P-glycoprotein (P-gp), a plasma membrane drug transporter (ABCB1, a member of the ABC transporter family), is the most prevalent cause of multidrug resistance in cancer tissues. Lectin concanavalin A (ConA) induces massive cell death of L1210 leukemia cells (S). Cell sublines of L1210 in which P-gp overexpression was induced by selection with vincristine (R) or by stable transfection with a plasmid encoding full-length human P-gp (T) were less sensitive to ConA. Both P-gp-positive cell lines exhibited typical P-gp-mediated multidrug resistance. Resistance of R and T cells to ConA was associated with lower binding of ConA as compared to S cells when analysed by the following methods: (i) SDS PAGE and electroblotting of proteins in the crude membrane fraction followed by detection with biotinylated ConA and avidin-peroxidase, and (ii) fluorescent cytometry or confocal microscopy of the intact cells with surfaces labeled by FITC-ConA. These data indicated that the presence of P-glycoprotein in L1210 cells independently of the mode of its expression induced down-regulation of cell surface saccharide targets of ConA. Therefore, this feature may be considered as a secondary cellular response to P-glycoprotein expression.

Expression of drug-transporting P-glycoprotein (P-gp, an integral protein of the plasma membrane) in neoplastic cells confers multidrug resistance and also involves alteration of cell sensitivity to inhibitors of the sarco/endoplasmic reticulum calcium pump thapsigargin (Th). Mouse leukaemia L1210 cell sublines that overexpress P-gp due to selection with vincristine (R) or stable transfection with a gene encoding human P-gp (T) were less sensitive to Th than the parental cell line (S). Th at a concentration of 0.1 μmol/l did not induce alterations in the amount of P-gp mRNA in R or T cells (S cells did not contain any measurable amount of this transcript as assessed by RT-PCR) or in the amount of calnexin (CNX) or glyceraldehyde-3-phosphate dehydrogenase (GAPDH) in all three cell sublines. However, when using a concentration of 10 μmol/l, Th decreases the amounts of CNX, GAPDH (in S, R and T cells) and P-gp (in R and T cells) mRNAs. In contrast to R and T cells (which contain abundant P-gp), S cells did not contain any P-gp detectable by the c219 antibody on a Western blot. Th at a concentration of 0.1 μmol/l induced a reduction in the amount of P-gp present in R and T cells, particularly in isoforms with higher molecular weights (i.e., mature fully glycosylated isoforms). Similar results were observed when Th was used at a concentration of 10 μmol/l. R and T cells contained lower levels of CNX than S cells. While Th at a lower concentration did not alter the levels of CNX in S, R or T cells, a higher concentration of this substance induced a measurable decrease in the amount of CNX. S, R and T cells did not differ with respect to GAPDH content, but Th induced a reduction in the amount of this protein in all cell sublines. More pronounced results were observed when Th was applied at a concentration of 10 μmol/l comparing with a concentration of 0.1 mmol/l. These changes may be involved together with the Th efflux activity of P-gp in Th-resistance associated with the P-gp-mediated multidrug resistance of R and T cells.

Carbonic anhydrase IX (CA IX) is a tumor-associated, hypoxia-induced enzyme involved in pH regulation and cell adhesion. Its catalytically active ectodomain (ECD) is linked to a transmembrane region and a short intracellular (IC) tail. Removal of the IC tail causes intracellular localization of CA IX. Mutations of basic amino acids within IC do not perturb the membrane position, but reduce shedding of the CA IX ectodomain as well as CA IX-mediated cell dissociation. Moreover, they abolish the CA IX capacity to acidify extracellular pH (pHe) and bind CA IX-selective sulfonamide inhibitor in hypoxia. These findings provide the first evidence for the critical contribution of the IC tail to the proper functioning of CA IX.