γ-Secretase-dependent cleavage of E-cadherin by staurosporine in breast cancer cells

The UBC9/SUMO pathway affects E-cadherin cleavage in HPV-positive head and neck cancer

Functional loss of E-cadherin is frequent during tumor progression and occurs through a variety of mechanisms, including proteolytic cleavage. E-cadherin downregulation leads to the conversion of a more malignant phenotype promoting Epithelial to Mesenchymal Transition (EMT). The UBC9/SUMO pathway has been also shown to be involved in the regulation of EMT in different cancers. Here we found an increased expression of UBC9 in the progression of Head and Neck Cancer (HNC) and uncovered a role for UBC9/SUMO in hampering the HPV-mediated E-cadherin cleavage in HNC.

γ-secretase inhibitors, DAPT and RO4929097, promote the migration of Human Glioma Cells via Smad5-downregulated E-cadherin Expression

Malignant gliomas are a type of central nervous system cancer with extremely high mortality rates in humans. γ-secretase has been becoming a potential target for cancer therapy, including glioma, because of the involvement of its enzymatic activity in regulating the proliferation and metastasis of cancer cells. In this study, we attempted to determine whether γ-secretase activity regulates E-cadherin to affect glioma cell migration. The human glioma cell lines, including LN18 and LN229, and the γ-secretase inhibitors, including N-[N-(3,5-difluorophenacetyl)-L-alanyl]-S-phenylglycine t-butyl ester (DAPT) and RO4929097, were used in this study. It was shown that γ-secretase activity inhibition by DAPT and RO4929097 could promote LN18 and LN229 glioma cell migration via downregulating E-cadherin mRNA and protein expressions, but not via affecting E-cadherin protein processing. In addition, γ-secretase activity inhibition was regulated by bone morphogenetic proteins-independent Smad5 activation in glioma cells. Moreover, endogenous Smad1 in glioma cells was found to play an important role in regulating E-cadherin expression and subsequent cell migration but did not affect DAPT-stimulated effects. These results help further elucidate the molecular mechanisms of γ-secretase activity regulation involved in controlling glioma cell malignancy. Information about a potential role for Smad1/5 activity upregulation and subsequent E-cadherin downregulation during inhibition of γ-secretase activity in the development of gliomas is therefore relevant for future research.

Activation of Notch signaling by soluble Dll4 decreases vascular permeability via a cAMP/PKA-dependent pathway

The Notch ligand delta-like ligand 4 (Dll4), upregulated by VEGF, is a key regulator of vessel morphogenesis and function, controlling tip and stalk cell selection during sprouting angiogenesis. Inhibition of Dll4 results in hypersprouting, nonfunctional, poorly perfused vessels, suggesting a role for Dll4 in the formation of mature, reactive, functional vessels, with low permeability and able to restrict fluid and solute exchange. We tested the hypothesis that Dll4 controls transvascular fluid exchange. A recombinant protein expressing only the extracellular portion of Dll4 [soluble Dll4 (sDll4)] induced Notch signaling in endothelial cells (ECs), resulting in increased expression of vascular-endothelial cadherin, but not the tight junctional protein zonula occludens 1, at intercellular junctions. sDll4 decreased the permeability of FITC-labeled albumin across EC monolayers, and this effect was abrogated by coculture with the γ-secretase inhibitor N-[N-(3,5-difluorophenacetyl)-l-alanyl]-S-phenylglycine t-butyl ester. One of the known molecular effectors responsible for strengthening EC-EC contacts is PKA, so we tested the effect of modulation of PKA on the sDll4-mediated reduction of permeability. Inhibition of PKA reversed the sDll4-mediated reduction in permeability and reduced expression of the Notch target gene Hey1. Knockdown of PKA reduced sDLL4-mediated vascular-endothelial cadherin junctional expression. sDll4 also caused a significant decrease in the hydraulic conductivity of rat mesenteric microvessels in vivo. This reduction was abolished upon coperfusion with the PKA inhibitor H89 dihydrochloride. These results indicate that Dll4 signaling through Notch activation acts through a cAMP/PKA pathway upon intercellular adherens junctions, but not tight junctions, to regulate endothelial barrier function. NEW & NOTEWORTHY Notch signaling reduces vascular permeability through stimulation of cAMP-dependent protein kinase A.

Epithelial Markers aSMA, Krt14, and Krt19 Unveil Elements of Murine Lacrimal Gland Morphogenesis and Maturation

As an element of the lacrimal apparatus, the lacrimal gland (LG) produces the aqueous part of the tear film, which protects the eye surface. Therefore, a defective LG can lead to serious eyesight impairment. Up to now, little is known about LG morphogenesis and subsequent maturation. In this study, we delineated elements of the cellular and molecular events involved in LG formation by using three epithelial markers, namely aSMA, Krt14, and Krt19. While aSMA marked a restricted epithelial population of the terminal end buds (TEBs) in the forming LG, Krt14 was found in the whole embryonic LG epithelial basal cell layer. Interestingly, Krt19 specifically labeled the presumptive ductal domain and subsequently, the luminal cell layer. By combining these markers, the Fucci reporter mouse strain and genetic fate mapping of the Krt14+ population, we demonstrated that LG epithelium expansion is fuelled by a patterned cell proliferation, and to a lesser extent by epithelial reorganization and possible mesenchymal-to-epithelial transition. We pointed out that this epithelial reorganization, which is associated with apoptosis, regulated the lumen formation. Finally, we showed that the inhibition of Notch signaling prevented the ductal identity from setting, and led to a LG covered by ectopic TEBs. Taken together our results bring a deeper understanding on LG morphogenesis, epithelial domain identity, and organ expansion.

Staurosporine enhances ATRA-induced granulocytic differentiation in human leukemia U937 cells via the MEK/ERK signaling pathway

Although all-trans retinoic acid (ATRA) is regarded as a prominent example of differentiation therapy, it is not effective for the treatment of other subtypes of acute myeloid leukemia (AML) beyond acute promyelocytic leukemia (APL). Therefore, new strategies need to be explored to extend the efficacy of ATRA-based therapy to non-APL AML patients. In the present study, staurosporine, a protein kinase C (PKC) pan-inhibitor, exhibited synergism with ATRA to promote granulocytic differentiation in poorly ATRA-sensitive U937 cells but not in ATRA unresponsive K562 and Kasumi cells. Staurosporine or the combined treatment did not affect PKC activity in U937 cells. Moreover, other selective PKC inhibitors, UCN-01, Go6976 or rottlerin failed to enhance ATRA‑induced granulocytic differentiation in U937 cells. Therefore, staurosporine-enhanced ATRA-induced granulocytic differentiation in U937 cells may be independent of PKC. Staurosporine activated mitogen‑activated protein kinase kinase (MEK) and extracellular signal‑regulated kinase (ERK). Meanwhile, staurosporine also enhanced ATRA-promoted upregulation of the protein level of CCAAT/enhancer‑binding protein β (C/EBPβ) and C/EBPε in U937 cells. Furthermore, blockade of MEK activation suppressed staurosporine‑enhanced differentiation as well as the elevated protein level of C/EBPs. Taken together, we concluded that staurosporine enhanced ATRA‑induced granulocytic differentiation in U937 cells via MEK/ERK-mediated modulation of the protein level of C/EBPs.

Urine survivin, E-cadherin and matrix metalloproteinases as novel biomarkers in children with chronic kidney disease

CONTEXT

Epithelial-mesenchymal transition (EMT) leads to renal fibrosis and chronic kidney disease (CKD).

OBJECTIVE

The aim of this study was to assess the usefulness of survivin, E-cadherin and metalloproteinases (MMPs) as biomarkers of CKD-related complications.

MATERIAL AND METHODS

Survivin, E-cadherin, MMP-2, MMP-9 and TGFbeta1 were assessed by ELISA in 41 children with CKD stages 3 to 5 and in 23 controls.

RESULTS

The serum and urine values of analyzed parameters were significantly elevated in CKD patients versus controls and correlated with each other.

CONCLUSIONS

The observed parameter changes indicate apoptosis, tissue remodeling and fibrosis in CKD children. Urine survivin may become a new biomarker of kidney-specific EMT.

Regulation of Notch 1 signaling in THP-1 cells enhances M2 macrophage differentiation

Macrophage polarization is emerging as an important area of research for the development of novel therapeutics to treat inflammatory diseases. Within the current study, the role of Notch1R in macrophage differentiation was investigated as well as downstream effects in THP-1 monocytes cultured in "inflammation mimicry" media. Interference of Notch signaling was achieved using either the pharmaceutical inhibitor DAPT or Notch1R small interfering RNA (siRNA), and Notch1R expression, macrophage phenotypes, and anti- and proinflammatory cytokine expression were evaluated. Data presented show that Notch1R expression on M1 macrophages as well as M1 macrophage differentiation is significantly elevated during cellular stress (P < 0.05). However, under identical culture conditions, interference to Notch signaling via Notch1R inhibition mitigated these results as well as promoted M2 macrophage differentiation. Moreover, when subjected to cellular stress, macrophage secretion of proinflammatory cytokines was significantly heightened (P < 0.05). Importantly, Notch1R inhibition not only diminished proinflammatory cytokine secretion but also enhanced anti-inflammatory protein release (P < 0.05). Our data suggest that Notch1R plays a pivotal role in M1 macrophage differentiation and heightened inflammatory responses. Therefore, we conclude that inhibition of Notch1R and subsequent downstream signaling enhances monocyte to M2 polarized macrophage outcomes and promotes anti-inflammatory mediation during cellular stress.

The impact of dialysis modality on novel markers of stress reaction, matrix remodeling and endothelial damage in children on chronic dialysis

BACKGROUND/AIMS

Dialysis triggers stress reaction, matrix remodeling and endothelial damage, but little is known about the changes it induces on selected heat shock proteins (Hsp90α), adhesion molecules (E-cadherin, sE-selectin), metalloproteinases (MMP-8) and their extracellular inducer (EMMPRIN). The aim of this study was to assess serum concentrations of the above-mentioned parameters in children on chronic dialysis.

METHODS

19 patients on hemodialysis (HD), 22 children on peritoneal dialysis (PD) and 30 age-matched controls were examined. Serum concentrations of parameters were assessed by ELISA.

RESULTS

Hsp90α, MMP-8, EMMPRIN and E-cadherin concentrations were significantly increased in children on dialysis vs. controls and higher levels were in HD than PD patients. There was no difference in the level of sE-selectin between HD and PD modalities. A single HD session diminished Hsp90α, MMP-8, EMMPRIN and E-cadherin values, but had no impact on sE-selectin levels.

CONCLUSIONS

Hemodialysis evokes stress reaction, matrix and endothelium destruction, to a greater extent than peritoneal dialysis. Single hemodialysis influences circulating cells rather than endothelial cells.

Cleavage of transmembrane junction proteins and their role in regulating epithelial homeostasis

Epithelial tissues form a selective barrier that separates the external environment from the internal tissue milieu. Single epithelial cells are densely packed and associate via distinct intercellular junctions. Intercellular junction proteins not only control barrier properties of the epithelium but also play an important role in regulating epithelial homeostasis that encompasses cell proliferation, migration, differentiation and regulated shedding. Recent studies have revealed that several proteases target epithelial junction proteins during physiological maturation as well as in pathologic states such as inflammation and cancer. This review discusses mechanisms and biological consequences of transmembrane junction protein cleavage. The influence of junction protein cleavage products on pathogenesis of inflammation and cancer is discussed.

New markers of apoptosis in children on chronic dialysis

Enhanced apoptosis is characteristic for chronic kidney disease (CKD). A specific type of apoptosis, anoikis, is connected with the extracellular matrix turnover and cell detachment. Although E-cadherin, extracellular matrix metalloproteinase inducer (EMMPRIN) and matrix metalloproteinase (MMP)-8 may play an important role in this process, they have not been analyzed in any nephrological aspect, either in CKD. The aim of study was to evaluate the serum concentrations of E-cadherin, EMMPRIN and their potential regulators (MMP-8, MMP-7, TIMP-1, TIMP-2), with relevance to apoptosis/cell damage markers (sFas, sFasL, Hsp27), in children with CKD. 39 CKD children stages 3–4, 26 CKD children stage 5 still on conservative treatment, 19 patients on hemodialysis (HD), 22 children on automated peritoneal dialysis (APD) and 30 controls were examined. Serum concentrations of those parameters were assessed by ELISA. Median E-cadherin, EMMPRIN and MMP-8 values were significantly increased in patients on dialysis versus those in pre-dialysis period and versus controls. The highest values were noticed in the HD subjects. Regression analysis revealed that EMMPRIN and MMP-8 predicted various apoptosis markers, whereas E-cadherin turned out the best predictor of both apoptosis (Hsp27, sFas, sFasL) and matrix turnover (MMP-7, TIMP-1, TIMP-2) indexes in dialyzed patients. Children with CKD are prone to E-cadherin, EMMPRIN and MMP-8 elevation, aggravated by the dialysis commencement and most evident on hemodialysis. Correlations between parameters suggest their role as indexes of apoptosis in children on dialysis. E-cadherin seems the most accurate marker of anoikis in this population.

Cadmium induces N-cadherin cleavage via ERK-mediated γ-secretase activation in C6 astroglia cells

N-cadherin has known to be involved in tumor progression and metastasis. However, it is still obscure about the signaling pathway involving in the processing of N-cadherin. Thus, we examined which signaling pathway plays a major role in the processing of N-cadherin in C6 glioma cells following treatment of cadmium (Cd), a highly ubiquitous heavy metal. A cleavage product of N-cadherin, N-cad/CTF2 was observed by the treatment of Cd to C6 cells in a time and concentration-dependent manner. The production of N-cad/CTF2 was inhibited by pretreatment of γ-secretase inhibitors or siRNA transfection of nicastrin, indicating that γ-secretase is involved in the cleavage. Interestingly, Cd could activate both ERK and JNK signaling pathways in C6 cells; however, γ-secretase-mediated N-cad/CTF2 production by Cd was completely blocked by MEK1/2 inhibitors PD184352 and U0126, but not by a JNK inhibitor SP600125, demonstrating that the ERK signaling pathway plays a major role in the cleavage. In addition, pretreatment of an antioxidant or Ca²⁺ blocker blocked the production of N-cad/CTF2 by Cd together with the inhibition of ERK1/2 phosphorylation. Collectively, these results suggest that Cd increases intracellular Ca²⁺ or ROS, which induces γ-secretase-dependent N-cad/CTF2 production via the activation of the ERK signaling pathway in C6 glial cells.