Endothelial-specific expression of WNK1 kinase is essential for angiogenesis and heart development in mice

Assessment of the Relationship Between the Six-Minute Walk Test (6MWT) With Serum Chloride Level and Mean Pulmonary Arterial Pressure in Patients With Pulmonary Arterial Hypertension

Pulmonary artery hypertension (PAH) is a fatal disease associated with high mortality, especially in countries with limited health resources in terms of lack of access to diagnostic and therapeutic evaluations. Therefore, it is necessary to discover inexpensive and available serum biomarkers for examining patients. This study investigates the relationship between PAH patients' six-minute walk (6MWT) distance, serum chloride levels, and mean pulmonary arterial pressure (mPAP). In this cross-sectional study, patients with PAH referring to the pulmonary hypertension clinic of our tertiary hospital were included. Then, the patient's demographic information and clinical findings were recorded, and the serum level of chloride and the 6MWT were examined in the patients. In the present study, 70 PAH patients were evaluated. All patients were female, and the mean age of the patients was 39.44 ± 8.33 years old. Hypochloremia was considered as serum chloride < 97 mmol/L in our study. The mPAP of patients with hypochloremia was significantly higher than non-hypochloremia patients (p < 0.001). The serum chloride levels had a significant positive correlation with the 6MWT distance (r = 0.634, p < 0.001). According to the linear regression analysis results, serum chloride level was a significant predictor of 6MWT distance even after adjustment for age and creatinine (β = 0.48; p = 0.002). Serum chloride level can be used as an inexpensive method for the evaluation of disease severity in PAH patients, especially in patients with higher time since the diagnosis of PAH.

WNK1-dependent water influx is required for CD4+ T cell activation and T cell-dependent antibody responses

Signaling from the T cell antigen receptor (TCR) on CD4+ T cells plays a critical role in adaptive immune responses by inducing T cell activation, proliferation, and differentiation. Here we demonstrate that WNK1, a kinase implicated in osmoregulation in the kidney, is required in T cells to support T-dependent antibody responses. We show that the canonical WNK1-OXSR1-STK39 kinase signaling pathway is required for TCR signaling in CD4+ T cells, their subsequent entry into the cell cycle, and suppression of the ATR-mediated G2/M cell cycle checkpoint. We show that the WNK1 pathway regulates ion influx leading to water influx, potentially through AQP3, and that water influx is required for TCR-induced signaling and cell cycle entry. Thus, TCR signaling via WNK1, OXSR1, STK39 and AQP3 leads to water entry that is essential for CD4+ T cell proliferation and hence T cell-dependent antibody responses.

Familial Hyperkalemic Hypertension

The rare disease Familial Hyperkalemic Hypertension (FHHt) is caused by mutations in the genes encoding Cullin 3 (CUL3), Kelch-Like 3 (KLHL3), and two members of the With-No-Lysine [K] (WNK) kinase family, WNK1 and WNK4. In the kidney, these mutations ultimately cause hyperactivation of NCC along the renal distal convoluted tubule. Hypertension results from increased NaCl retention, and hyperkalemia by impaired K + secretion by downstream nephron segments. CUL3 and KLHL3 are now known to form a ubiquitin ligase complex that promotes proteasomal degradation of WNK kinases, which activate downstream kinases that phosphorylate and thus activate NCC. For CUL3, potent effects on the vasculature that contribute to the more severe hypertensive phenotype have also been identified. Here we outline the in vitro and in vivo studies that led to the discovery of the molecular pathways regulating NCC and vascular tone, and how FHHt-causing mutations disrupt these pathways. Potential mechanisms for variability in disease severity related to differential effects of each mutation on the kidney and vasculature are described, and other possible effects of the mutant proteins beyond the kidney and vasculature are explored. © 2024 American Physiological Society. Compr Physiol 14:5839-5874, 2024.

Zebrafish model for functional screening of flow-responsive genes controlling endothelial cell proliferation

Local haemodynamics control arterial homeostasis and dysfunction by generating wall shear stress (WSS) which regulates endothelial cell (EC) physiology. Here we use a zebrafish model to identify genes that regulate EC proliferation in response to flow. Suppression of blood flow in zebrafish embryos (by targeting cardiac troponin) reduced EC proliferation in the intersegmental vessels (ISVs) compared to controls exposed to flow. The expression of candidate regulators of proliferation was analysed in EC isolated from zebrafish embryos by qRT-PCR. Genes shown to be expressed in EC were analysed for the ability to regulate proliferation in zebrafish vasculature exposed to flow or no-flow conditions using a knockdown approach. wnk1 negatively regulated proliferation in no-flow conditions, whereas fzd5, gsk3β, trpm7 and bmp2a promoted proliferation in EC exposed to flow. Immunofluorescent staining of mammalian arteries revealed that WNK1 is expressed at sites of low WSS in the murine aorta, and in EC overlying human atherosclerotic plaques. We conclude that WNK1 is expressed in EC at sites of low WSS and in diseased arteries and may influence vascular homeostasis by reducing EC proliferation.

SMURF1/2 are novel regulators of WNK1 stability

Angiogenesis is essential for remodeling and repairing existing vessels, and this process requires signaling pathways including those controlled by transforming growth factor beta (TGF-β). We have previously reported crosstalk between TGF-β and the protein kinase With No lysine (K) 1 (WNK1). Homozygous disruption of the gene encoding WNK1 results in lethality in mice near embryonic day E12 due to impaired angiogenesis and this defect can be rescued by endothelial-specific expression of an activated form of the WNK1 substrate kinase Oxidative Stress-Responsive 1 (OSR1). However, molecular processes regulated via a collaboration between TGF-β and WNK1/OSR1 are not well understood. Here we show that WNK1 interacts with the E3 ubiquitin ligases SMURF1/2. In addition, we discovered that WNK1 regulates SMURF1/2 protein stability and vice versa. We also demonstrate that WNK1 activity regulates TGF-β receptor levels, in turn, controlling TGF-β signaling.

Cullin 3/with No Lysine [K] Kinase/Ste20/SPS-Related Proline Alanine Rich Kinase Signaling: Impact on NaCl Cotransporter Activity in BP Regulation

The sodium chloride cotransporter (NCC) fine-tunes Na + balance and indirectly affects the homeostasis of other ions including K + , Mg 2+ , and Ca 2+ . Owing to its effects on Na + balance, BP is significantly affected by alterations in NCC activity. Several factors have been reported to influence the expression and activity of NCC. One critical factor is NCC phosphorylation/dephosphorylation that occurs at key serine-threonine amino acid residues of the protein. Phosphorylation, which results in increased NCC activity, is mediated by the with no lysine [K] (WNK)-SPS-related proline alanine rich kinase (SPAK)/OSR1 kinases. NCC activation stimulates reabsorption of Na + , increasing extracellular fluid volume and hence BP. On the other hand, proteasomal degradation of WNK kinases after ubiquitination by the Cullin 3-Kelch-like 3 E3 ubiquitin ligase complex and dephosphorylation pathways oppose WNK-SPAK/OSR1-mediated NCC activation. Components of the Cullin 3/Kelch-like 3-WNK-SPAK/OSR1 regulatory pathway may be targets for novel antihypertensive drugs. In this review, we outline the impact of these regulators on the activity of NCC and the consequent effect on BP.

A New Phase for WNK Kinase Signaling Complexes as Biomolecular Condensates

The purpose of this review is to highlight transformative advances that have been made in the field of biomolecular condensates, with special emphasis on condensate material properties, physiology, and kinases, using the With-No-Lysine (WNK) kinases as a prototypical example. To convey how WNK kinases illustrate important concepts for biomolecular condensates, we start with a brief history, focus on defining features of biomolecular condensates, and delve into some examples of how condensates are implicated in cellular physiology (and pathophysiology). We then highlight how WNK kinases, through the action of "WNK droplets" that ubiquitously regulate intracellular volume and kidney-specific "WNK bodies" that are implicated in distal tubule salt reabsorption and potassium homeostasis, exemplify many of the defining features of condensates. Finally, this review addresses the controversies within this emerging field and questions to address.

L-Wnk1 Deletion in Smooth Muscle Cells Causes Aortitis and Inflammatory Shift

BACKGROUND

The long isoform of the Wnk1 (with-no-lysine [K] kinase 1) is a ubiquitous serine/threonine kinase, but its role in vascular smooth muscle cells (VSMCs) pathophysiology remains unknown.

METHODS

AngII (angiotensin II) was infused in Apoe-/- to induce experimental aortic aneurysm. Mice carrying an Sm22-Cre allele were cross-bred with mice carrying a floxed Wnk1 allele to specifically investigate the functional role of Wnk1 in VSMCs.

RESULTS

Single-cell RNA-sequencing of the aneurysmal abdominal aorta from AngII-infused Apoe-/- mice revealed that VSMCs that did not express Wnk1 showed lower expression of contractile phenotype markers and increased inflammatory activity. Interestingly, WNK1 gene expression in VSMCs was decreased in human abdominal aortic aneurysm. Wnk1-deficient VSMCs lost their contractile function and exhibited a proinflammatory phenotype, characterized by the production of matrix metalloproteases, as well as cytokines and chemokines, which contributed to local accumulation of inflammatory macrophages, Ly6Chi monocytes, and γδ T cells. Sm22Cre+Wnk1lox/lox mice spontaneously developed aortitis in the infrarenal abdominal aorta, which extended to the thoracic area over time without any negative effect on long-term survival. AngII infusion in Sm22Cre+Wnk1lox/lox mice aggravated the aortic disease, with the formation of lethal abdominal aortic aneurysms. Pharmacological blockade of γδ T-cell recruitment using neutralizing anti-CXCL9 (anti-CXC motif chemokine ligand 9) antibody treatment, or of monocyte/macrophage using Ki20227, a selective inhibitor of CSF1 receptor, attenuated aortitis. Wnk1 deletion in VSMCs led to aortic wall remodeling with destruction of elastin layers, increased collagen content, and enhanced local TGF-β (transforming growth factor-beta) 1 expression. Finally, in vivo TGF-β blockade using neutralizing anti-TGF-β antibody promoted saccular aneurysm formation and aorta rupture in Sm22 Cre+ Wnk1lox/lox mice but not in control animals.

CONCLUSION

Wnk1 is a key regulator of VSMC function. Wnk1 deletion promotes VSMC phenotype switch toward a pathogenic proinflammatory phenotype, orchestrating deleterious vascular remodeling and spontaneous severe aortitis in mice.

Predictive and Experimental Motif Interaction Analysis Identifies Functions of the WNK-OSR1/SPAK Pathway

The WNK-OSR1/SPAK protein kinase signaling pathway regulates ion homeostasis and cell volume, but its other functions are poorly understood. To uncover undefined signaling functions of the pathway we analyzed the binding specificity of the conserved C-terminal (CCT) domains of OSR1 and SPAK to find all possible interaction motifs in human proteins. These kinases bind the core consensus sequences R-F-x-V/I and R-x-F-x-V/I. Motifs were ranked based on sequence, conservation, cellular localization, and solvent accessibility. Out of nearly 3,700 motifs identified, 90% of previously published motifs were within the top 2% of those predicted. Selected candidates (TSC22D1, CAVIN1, ATG9A, NOS3, ARHGEF5) were tested. Upstream kinases WNKs 1-4 and their close relatives, the pseudokinases NRBP1/2, contain CCT-like domains as well. We identified additional distinct motif variants lacking the conserved arginine previously thought to be required, and found that the NRBP1 CCT-like domain binds TSC22D1 via the same motif as OSR1 and SPAK. Our results further highlight the rich and diverse functionality of CCT and CCT-like domains in connecting WNK signaling to cellular processes.

Dihydrotestosterone Augments the Angiogenic and Migratory Potential of Human Endothelial Progenitor Cells by an Androgen Receptor-Dependent Mechanism

Endothelial progenitor cells (EPCs) play a critical role in cardiovascular regeneration. Enhancement of their native properties would be highly beneficial to ensuring the proper functioning of the cardiovascular system. As androgens have a positive effect on the cardiovascular system, we hypothesized that dihydrotestosterone (DHT) could also influence EPC-mediated repair processes. To evaluate this hypothesis, we investigated the effects of DHT on cultured human EPCs' proliferation, viability, morphology, migration, angiogenesis, gene and protein expression, and ability to integrate into cardiac tissue. The results showed that DHT at different concentrations had no cytotoxic effect on EPCs, significantly enhanced the cell proliferation and viability and induces fast, androgen-receptor-dependent formation of capillary-like structures. DHT treatment of EPCs regulated gene expression of androgen receptors and the genes and proteins involved in cell migration and angiogenesis. Importantly, DHT stimulation promoted EPC migration and the cells' ability to adhere and integrate into murine cardiac slices, suggesting it has a role in promoting tissue regeneration. Mass spectrometry analysis further highlighted the impact of DHT on EPCs' functioning. In conclusion, DHT increases the proliferation, migration, and androgen-receptor-dependent angiogenesis of EPCs; enhances the cells' secretion of key factors involved in angiogenesis; and significantly potentiates cellular integration into heart tissue. The data offer support for potential therapeutic applications of DHT in cardiovascular regeneration and repair processes.

WNK kinase is a vasoactive chloride sensor in endothelial cells

Endothelial cells (ECs) line the wall of blood vessels and regulate arterial contractility to tune regional organ blood flow and systemic pressure. Chloride (Cl-) is the most abundant anion in ECs and the Cl- sensitive With-No-Lysine (WNK) kinase is expressed in this cell type. Whether intracellular Cl- signaling and WNK kinase regulate EC function to alter arterial contractility is unclear. Here, we tested the hypothesis that intracellular Cl- signaling in ECs regulates arterial contractility and examined the signaling mechanisms involved, including the participation of WNK kinase. Our data obtained using two-photon microscopy and cell-specific inducible knockout mice indicated that acetylcholine, a prototypical vasodilator, stimulated a rapid reduction in intracellular Cl- concentration ([Cl-]i) due to the activation of TMEM16A, a Cl- channel, in ECs of resistance-size arteries. TMEM16A channel-mediated Cl- signaling activated WNK kinase, which phosphorylated its substrate proteins SPAK and OSR1 in ECs. OSR1 potentiated transient receptor potential vanilloid 4 (TRPV4) currents in a kinase-dependent manner and required a conserved binding motif located in the channel C terminus. Intracellular Ca2+ signaling was measured in four dimensions in ECs using a high-speed lightsheet microscope. WNK kinase-dependent activation of TRPV4 channels increased local intracellular Ca2+ signaling in ECs and produced vasodilation. In summary, we show that TMEM16A channel activation reduces [Cl-]i, which activates WNK kinase in ECs. WNK kinase phosphorylates OSR1 which then stimulates TRPV4 channels to produce vasodilation. Thus, TMEM16A channels regulate intracellular Cl- signaling and WNK kinase activity in ECs to control arterial contractility.

T cell migration requires ion and water influx to regulate actin polymerization

Migration of T cells is essential for their ability to mount immune responses. Chemokine-induced T cell migration requires WNK1, a kinase that regulates ion influx into the cell. However, it is not known why ion entry is necessary for T cell movement. Here we show that signaling from the chemokine receptor CCR7 leads to activation of WNK1 and its downstream pathway at the leading edge of migrating CD4+ T cells, resulting in ion influx and water entry by osmosis. We propose that WNK1-induced water entry is required to swell the membrane at the leading edge, generating space into which actin filaments can polymerize, thereby facilitating forward movement of the cell. Given the broad expression of WNK1 pathway proteins, our study suggests that ion and water influx are likely to be essential for migration in many cell types, including leukocytes and metastatic tumor cells.

Unanticipated domain requirements for Drosophila Wnk kinase in vivo

WNK (With no Lysine [K]) kinases have critical roles in the maintenance of ion homeostasis and the regulation of cell volume. Their overactivation leads to pseudohypoaldosteronism type II (Gordon syndrome) characterized by hyperkalemia and high blood pressure. More recently, WNK family members have been shown to be required for the development of the nervous system in mice, zebrafish, and flies, and the cardiovascular system of mice and fish. Furthermore, human WNK2 and Drosophila Wnk modulate canonical Wnt signaling. In addition to a well-conserved kinase domain, animal WNKs have a large, poorly conserved C-terminal domain whose function has been largely mysterious. In most but not all cases, WNKs bind and activate downstream kinases OSR1/SPAK, which in turn regulate the activity of various ion transporters and channels. Here, we show that Drosophila Wnk regulates Wnt signaling and cell size during the development of the wing in a manner dependent on Fray, the fly homolog of OSR1/SPAK. We show that the only canonical RF(X)V/I motif of Wnk, thought to be essential for WNK interactions with OSR1/SPAK, is required to interact with Fray in vitro. However, this motif is unexpectedly dispensable for Fray-dependent Wnk functions in vivo during fly development and fluid secretion in the Malpighian (renal) tubules. In contrast, a structure function analysis of Wnk revealed that the less-conserved C-terminus of Wnk, that recently has been shown to promote phase transitions in cell culture, is required for viability in vivo. Our data thus provide novel insights into unexpected in vivo roles of specific WNK domains.

WNK1 mediates amphiregulin-induced MMP9 expression and cell invasion in human extravillous trophoblast cells

The invasion of human extravillous trophoblast (EVT) cells is a critical event required for a successful pregnancy. Amphiregulin, a ligand of the epidermal growth factor receptor (EGFR), has been shown to stimulate cell invasion in an immortalized human EVT cell line, HTR-8/SVneo. The with-no-lysine kinase 1 (WNK1) is involved in regulating cell invasion. It is known that WNK1 is expressed in the human placenta, but its role in human EVT cells remains unknown. In the present study, we show that AREG treatment phosphorylated WNK1 at Thr60 in both HTR-8/SVneo and primary human EVT cells. The stimulatory effect of AREG on WNK1 phosphorylation was mediated by the activation of PI3K/AKT, but not the ERK1/2 signaling pathway. AREG upregulated matrix metalloproteinase 9 (MMP9) but not MMP2. In addition, cell invasiveness was increased in response to the treatment of AREG. Using the siRNA-mediated knockdown approach, our results showed that the knockdown of WNK1 attenuated the AREG-induced upregulation of MMP9 expression and cell invasion. Moreover, the expression of WNK1 was downregulated in the placentas with preeclampsia, a disease resulting from insufficiency of EVT cell invasion during pregnancy. This study discovers the physiological function of WNK1 in human EVT cells and provides important insights into the regulation of MMP9 and cell invasion in human EVT cells.

WNK1 is required during male pachynema to sustain fertility

WNK1 is an important regulator in many physiological functions, yet its role in male reproduction is unexplored. In the male germline, WNK1 is upregulated in preleptotene spermatocytes indicating possible function(s) in spermatogenic meiosis. Indeed, deletion of Wnk1 in mid-pachytene spermatocytes using the Wnt7a-Cre mouse led to male sterility which resembled non-obstructive azoospermia in humans, where germ cells failed to complete spermatogenesis and produced no sperm. Mechanistically, we found elevated MTOR expression and signaling in the Wnk1-depleted spermatocytes. As MTOR is a central mediator of translation, we speculated that translation may be accelerated in these spermatocytes. Supporting this, we found the acrosome protein, ACRBP to be prematurely expressed in the spermatocytes with Wnk1 deletion. Our study uncovered an MTOR-regulating factor in the male germline with potential implications in translation, and future studies will aim to understand how WNK1 regulates MTOR activity and impact translation on a broader spectrum.

Regulatory role of PI3K/Akt/WNK1 signal pathway in mouse model of bone cancer pain

In the advanced stage of cancer, the pain caused by bone metastasis is unbearable, but the mechanism of bone cancer pain (BCP) is very complicated and remains unclear. In this study, we used 4T1 mouse breast cancer cells to establish a bone cancer pain model to study the mechanism of BCP. Then the paw withdrawal mechanical threshold (PWMT) and the hematoxylin-eosin staining were used to reflect the erosion of cancer cells on tibia tissue. We also determined the role of proinflammatory factors (TNF-α, IL-17, etc.) in BCP by the enzyme-linked immunosorbent assay in mouse serum. When GSK690693, a new Akt inhibitor, was given and the absence of intermediate signal dominated by Akt is found, pain may be relieved by blocking the transmission of pain signal and raising the PWMT. In addition, we also found that GSK690693 inhibited the phosphorylation of Akt protein, resulting in a significant decrease in with-nolysinekinases 1 (WNK1) expression in the spinal cord tissue. In the BCP model, we confirmed that GSK690693 has a relieving effect on BCP, which may play an analgesic effect through PI3K-WNK1 signal pathway. At the same time, there is a close relationship between inflammatory factors and PI3K-WNK1 signal pathway. The PI3K/Akt pathway in the dorsal horn of the mouse spinal cord activates the downstream WNK1 protein, which promotes the release of inflammatory cytokines, which leads to the formation of BCP in mice. Inhibition of Akt can reduce the levels of IL-17 and TNF-α, cut off the downstream WNK1 protein signal receiving pathway, increase the PWMT and relieve BCP in mice. To clarify the analgesic target of BCP, to provide reference and theoretical support for the clinical effective treatment of BCP and the development of new high-efficiency analgesics.

WNK1 promotes water homeostasis by acting as a central osmolality sensor for arginine vasopressin release

Maintaining internal osmolality constancy is essential for life. Release of arginine vasopressin (AVP) in response to hyperosmolality is critical. Current hypotheses for osmolality sensors in circumventricular organs (CVOs) of the brain focus on mechanosensitive membrane proteins. The present study demonstrated that intracellular protein kinase WNK1 was involved. Focusing on vascular-organ-of-lamina-terminalis (OVLT) nuclei, we showed that WNK1 kinase was activated by water restriction. Neuron-specific conditional KO (cKO) of Wnk1 caused polyuria with decreased urine osmolality that persisted in water restriction and blunted water restriction-induced AVP release. Wnk1 cKO also blunted mannitol-induced AVP release but had no effect on osmotic thirst response. The role of WNK1 in the osmosensory neurons in CVOs was supported by neuronal pathway tracing. Hyperosmolality-induced increases in action potential firing in OVLT neurons was blunted by Wnk1 deletion or pharmacological WNK inhibitors. Knockdown of Kv3.1 channel in OVLT by shRNA reproduced the phenotypes. Thus, WNK1 in osmosensory neurons in CVOs detects extracellular hypertonicity and mediates the increase in AVP release by activating Kv3.1 and increasing action potential firing from osmosensory neurons.

WNK1 enforces macrophage lineage fidelity

The appropriate development of macrophages, the body's professional phagocyte, is essential for organismal development, especially in mammals. This dependence is exemplified by the observation that loss-of-function mutations in colony stimulating factor 1 receptor (CSF1R) results in multiple tissue abnormalities owing to an absence of macrophages. Despite this importance, little is known about the molecular and cell biological regulation of macrophage development. Here, we report the surprising finding that the chloride-sensing kinase With-no-lysine 1 (WNK1) is required for development of tissue-resident macrophages (TRMs). Myeloid-specific deletion of Wnk1 resulted in a dramatic loss of TRMs, disrupted organ development, systemic neutrophilia, and mortality between 3 and 4 weeks of age. Strikingly, we found that myeloid progenitors or precursors lacking WNK1 not only failed to differentiate into macrophages, but instead differentiated into neutrophils. Mechanistically, the cognate CSF1R cytokine macrophage-colony stimulating factor (M-CSF) stimulates macropinocytosis by both mouse and human myeloid progenitors and precursor cells. Macropinocytosis, in turn, induces chloride flux and WNK1 phosphorylation. Importantly, blocking macropinocytosis, perturbing chloride flux during macropinocytosis, and inhibiting WNK1 chloride-sensing activity each skewed myeloid progenitor differentiation from macrophages into neutrophils. Thus, we have elucidated a role for WNK1 during macropinocytosis and discovered a novel function of macropinocytosis in myeloid progenitors and precursor cells to ensure macrophage lineage fidelity.

Highlights

Myeloid-specific WNK1 loss causes failed macrophage development and premature deathM-CSF-stimulated myeloid progenitors and precursors become neutrophils instead of macrophagesM-CSF induces macropinocytosis by myeloid progenitors, which depends on WNK1Macropinocytosis enforces macrophage lineage commitment.

B cell-intrinsic requirement for WNK1 kinase in antibody responses in mice

Migration and adhesion play critical roles in B cells, regulating recirculation between lymphoid organs, migration within lymphoid tissue, and interaction with CD4+ T cells. However, there is limited knowledge of how B cells integrate chemokine receptor and integrin signaling with B cell activation to generate efficient humoral responses. Here, we show that the WNK1 kinase, a regulator of migration and adhesion, is essential in B cells for T-dependent and -independent antibody responses. We demonstrate that WNK1 transduces signals from the BCR, CXCR5, and CD40, and using intravital imaging, we show that WNK1 regulates migration of naive and activated B cells, and their interactions with T cells. Unexpectedly, we show that WNK1 is required for BCR- and CD40-induced proliferation, acting through the OXSR1 and STK39 kinases, and for efficient B cell-T cell collaboration in vivo. Thus, WNK1 is critical for humoral immune responses, by regulating B cell migration, adhesion, and T cell-dependent activation.

A metazoan-specific C-terminal motif in EXC-4 and Gα-Rho/Rac signaling regulate cell outgrowth during tubulogenesis in C. elegans

Chloride intracellular channels (CLICs) are conserved proteins for which the cellular and molecular functions remain mysterious. An important insight into CLIC function came from the discovery that Caenorhabditis elegans EXC-4/CLIC regulates morphogenesis of the excretory canal (ExCa) cell, a single-cell tube. Subsequent work showed that mammalian CLICs regulate vascular development and angiogenesis, and human CLIC1 can rescue exc-4 mutants, suggesting conserved function in biological tube formation (tubulogenesis) and maintenance. However, the cell behaviors and signaling pathways regulated by EXC-4/CLICs during tubulogenesis in vivo remain largely unknown. We report a new exc-4 mutation, affecting a C-terminal residue conserved in virtually all metazoan CLICs, that reveals a specific role for EXC-4 in ExCa outgrowth. Cell culture studies suggest a function for CLICs in heterotrimeric G protein (Gα/β/γ)-Rho/Rac signaling, and Rho-family GTPases are common regulators of cell outgrowth. Using our new exc-4 mutant, we describe a previously unknown function for Gα-encoding genes (gpa-12/Gα12/13, gpa-7/Gαi, egl-30/Gαq and gsa-1/Gαs), ced-10/Rac and mig-2/RhoG in EXC-4-mediated ExCa outgrowth. Our results demonstrate that EXC-4/CLICs are primordial players in Gα-Rho/Rac-signaling, a pathway that is crucial for tubulogenesis in C. elegans and in vascular development.

WNK1–OSR1 Signaling Regulates Angiogenesis-Mediated Metastasis towards Developing a Combinatorial Anti-Cancer Strategy

Lysine-deficient protein kinase-1 (WNK1) is critical for both embryonic angiogenesis and tumor-induced angiogenesis. However, the downstream effectors of WNK1 during these processes remain ambiguous. In this study, we identified that oxidative stress responsive 1b (osr1b) is upregulated in endothelial cells in both embryonic and tumor-induced angiogenesis in zebrafish, accompanied by downregulation of protein phosphatase 2A (pp2a) subunit ppp2r1bb. In addition, wnk1a and osr1b are upregulated in two liver cancer transgenic fish models: [tert x p53^−/−] and [HBx,src,p53^−/−,RPIA], while ppp2r1bb is downregulated in [tert x p53^−/−]. Furthermore, using HUVEC endothelial cells co-cultured with HepG2 hepatoma cells, we confirmed that WNK1 plays a critical role in the induction of hepatoma cell migration in both endothelial cells and hepatoma cells. Moreover, overexpression of OSR1 can rescue the reduced cell migration caused by shWNK1 knockdown in HUVEC cells, indicating OSR1 is downstream of WNK1 in endothelial cells promoting hepatoma cell migration. Overexpression of PPP2R1A can rescue the increased cell migration caused by WNK1 overexpression in HepG2, indicating that PPP2R1A is a downstream effector in hepatoma. The combinatorial treatment with WNK1 inhibitor (WNK463) and OSR1 inhibitor (Rafoxanide) plus oligo-fucoidan via oral gavage to feed [HBx,src,p53^−/−,RPIA] transgenic fish exhibits much more significant anticancer efficacy than Regorafenib for advanced HCC. Importantly, oligo-fucoidan can reduce the cell senescence marker-IL-1β expression. Furthermore, oligo-fucoidan reduces the increased cell senescence-associated β-galactosidase activity in tert transgenic fish treated with WNK1-OSR1 inhibitors. Our results reveal the WNK1–OSR1–PPP2R1A axis plays a critical role in both endothelial and hepatoma cells during tumor-induced angiogenesis promoting cancer cell migration. By in vitro and in vivo experiments, we further uncover the molecular mechanisms of WNK1 and its downstream effectors during tumor-induced angiogenesis. Targeting WNK1–OSR1-mediated anti-angiogenesis and anti-cancer activity, the undesired inflammation response caused by inhibiting WNK1–OSR1 can be attenuated by the combination therapy with oligo-fucoidan and may improve the efficacy.

An update regarding the role of WNK kinases in cancer

Mammalian WNK kinases (WNKs) are serine/threonine kinases that contain four members, WNK1-4. They function to maintain ion homeostasis and regulate blood pressure in mammals. Recent studies have revealed that the dysregulation of WNKs contributes to tumor growth, metastasis, and angiogenesis through complex mechanisms, especially through phosphorylating kinase substrates SPS1-related proline/alanine-rich kinase (SPAK) and oxidative stress-responsive kinase 1 (OSR1). Here, we review and discuss the relationships between WNKs and several key factors/biological processes in cancer, including ion channels, cation chloride cotransporters, sodium bicarbonate cotransporters, signaling pathways, angiogenesis, autophagy, and non-coding RNAs. In addition, the potential drugs for targeting WNK-SPAK/OSR1 signaling have also been discussed. This review summarizes and discusses knowledge of the roles of WNKs in cancer, which provides a comprehensive reference for future studies.

WNK1 collaborates with TGF-β in endothelial cell junction turnover and angiogenesis

Angiogenesis is essential for growth of new blood vessels, remodeling existing vessels, and repair of damaged vessels, and these require reorganization of endothelial cell-cell junctions through a partial endothelial-mesenchymal transition. Homozygous disruption of the gene encoding the protein kinase WNK1 results in lethality in mice near embryonic day (E) 12 due to impaired angiogenesis. This angiogenesis defect can be rescued by endothelial-specific expression of an activated form of the WNK1 substrate kinase OSR1. We show that inhibition of WNK1 kinase activity not only prevents sprouting of endothelial cells from aortic slices but also vessel extension in inhibitor-treated embryos ex vivo. Mutations affecting TGF-β signaling also result in abnormal vascular development beginning by E10 and, ultimately, embryonic lethality. Previously, we demonstrated cross-talk of WNK1 with TGF-β-regulated SMAD signaling, and OSR1 was identified as a component of the TGF-β interactome. However, molecular events jointly regulated by TGF-β and WNK1/OSR1 have not been delineated. Here, we show that inhibition of WNK1 promotes TGF-β-dependent degradation of the tyrosine kinase receptor AXL, which is involved in TGF-β-mediated cell migration and angiogenesis. We also show that interaction between OSR1 and occludin, a protein associated with endothelial tight junctions, is an essential step to enable tight junction turnover. Furthermore, we show that these phenomena are WNK1 dependent, and sensitive to TGF-β. These findings demonstrate intimate connections between WNK1/OSR1 and multiple TGF-β-sensitive molecules controlling angiogenesis and suggest that WNK1 may modulate many TGF-β-regulated functions.

WNK1 in Malignant Behaviors: A Potential Target for Cancer?

Metastasis is the major cause of mortality in cancer patients. Analyses of mouse models and patient data have implicated the protein kinase WNK1 as one of a handful of genes uniquely linked to a subset of invasive cancers. WNK1 signaling pathways are widely implicated in the regulation of ion co-transporters and in controlling cell responses to osmotic stress. In this review we will discuss its actions in tumor malignancy in human cancers and present evidence for its function in invasion, migration, angiogenesis and mesenchymal transition.

UBR5 is a novel regulator of WNK1 stability

The with no lysine (K) 1 (WNK1) protein kinase maintains cellular ion homeostasis in many tissues through actions on ion cotransporters and channels. Increased accumulation of WNK1 protein leads to pseudohypoaldosteronism type II (PHAII), a form of familial hypertension. WNK1 can be degraded via its adaptor-dependent recruitment to the Cullin3-RBX1 E3 ligase complex by the ubiquitin-proteasome system. Disruption of this process also leads to disease. To determine if this is the primary mechanism of WNK1 turnover, we examined WNK1 protein stability and degradation by measuring its rate of decay after blockade of translation. Here, we show that WNK1 protein degradation exhibits atypical kinetics in Hela cells. Consistent with this apparent complexity, we found that multiple degradative pathways can modulate cellular WNK1 protein amount. WNK1 protein is degraded not only by the proteasome, but also by the lysosome. Non-lysosomal cysteine proteases calpain and caspases also influence WNK1 degradation, as inhibitors of these proteases modestly increased WNK1 protein expression. Importantly, we discovered that the E3 ubiquitin ligase UBR5 interacts with WNK1 and its deficiency results in increased WNK1 protein. Our results further demonstrate that increased WNK1 in UBR5-depleted cells is attributable to reduced lysosomal degradation of WNK1 protein. Taken together, our findings provide insights into the multiplicity of degradative pathways involved in WNK1 turnover and uncover UBR5 as a previously unknown regulator of WNK1 protein stability that leads to lysosomal degradation of WNK1 protein.

CCT and CCT-Like Modular Protein Interaction Domains in WNK Signaling

The WNK [with no lysine (K)] kinases and their downstream effector kinases, oxidative stress responsive 1 (OSR1) and SPS/STE20-related proline-alanine-rich kinase (SPAK), have well established functions in the maintenance of cell volume and ion homeostasis. Mutations in these kinases have been linked to an inherited form of hypertension, neurologic defects, and other pathologies. A rapidly expanding body of evidence points to the involvement of WNKs in regulating multiple diverse cellular processes as well as the progression of some forms of cancer. How OSR1 and SPAK contribute to these processes is well understood in some cases but completely unknown in others. OSR1 and SPAK are targeted to both WNKs and substrates via their conserved C-terminal (CCT) protein interaction domains. Considerable effort has been put forth to understand the structure, function, and interaction specificity of the CCT domains in relation to WNK signaling, and multiple inhibitors of WNK signaling target these domains. The domains bind RFxV and RxFxV protein sequence motifs with the consensus sequence R-F-x-V/I or R-x-F-x-V/I, but residues outside the core motif also contribute to specificity. CCT interactions are required for OSR1 and SPAK activation and deactivation as well as cation-chloride cotransporter substrate phosphorylation. All four WNKs also contain CCT-like domains that have similar structures and conserved binding residues when compared with CCT domains, but their functions and interaction specificities are mostly unknown. A better understanding of the varied actions of these domains and their interactions will better define the known signaling mechanisms of the WNK pathway as well as uncover new ones. SIGNIFICANCE STATEMENT: WNK [with no lysine (K)] kinases and their downstream effector kinases, oxidative stress responsive 1 (OSR1) and SPS/STE20-related proline-alanine-rich kinase (SPAK), have been shown to be involved in an array of diverse cellular processes. Here we review the function of modular protein interaction domains found in OSR1 and SPAK as well as related domains found in WNKs.

L-WNK1 is required for BK channel activation in intercalated cells

Large-conductance K+ (BK) channels expressed in intercalated cells (ICs) in the aldosterone-sensitive distal nephron (ASDN) mediate flow-induced K+ secretion. In the ASDN of mice and rabbits, IC BK channel expression and activity increase with a high-K+ diet. In cell culture, the long isoform of with-no-lysine kinase 1 (L-WNK1) increases BK channel expression and activity. Apical L-WNK1 expression is selectively enhanced in ICs in the ASDN of rabbits on a high-K+ diet, suggesting that L-WNK1 contributes to BK channel regulation by dietary K+. We examined the role of IC L-WNK1 expression in enhancing BK channel activity in response to a high-K+ diet. Mice with IC-selective deletion of L-WNK1 (IC-L-WNK1-KO) and littermate control mice were placed on a high-K+ (5% K+, as KCl) diet for 10 or more days. IC-L-WNK1-KO mice exhibited reduced IC apical + subapical α-subunit expression and BK channel-dependent whole cell currents compared with controls. Six-hour urinary K+ excretion in response a saline load was similar in IC-L-WNK1-KO mice and controls. The observations that IC-L-WNK1-KO mice on a high-K+ diet have higher blood K+ concentration and reduced IC BK channel activity are consistent with impaired urinary K+ secretion, demonstrating that IC L-WNK1 has a role in the renal adaptation to a high-K+ diet.NEW & NOTEWORTHY When mice are placed on a high-K+ diet, genetic disruption of the long form of with no lysine kinase 1 (L-WNK1) in intercalated cells reduced relative apical + subapical localization of the large-conductance K+ channel, blunted large-conductance K+ channel currents in intercalated cells, and increased blood K+ concentration. These data confirm an in vivo role of L-WNK1 in intercalated cells in adaptation to a high-K+ diet.

Chloride sensing by WNK1 regulates NLRP3 inflammasome activation and pyroptosis

The NLRP3 inflammasome mediates the production of proinflammatory cytokines and initiates inflammatory cell death. Although NLRP3 is essential for innate immunity, aberrant NLRP3 inflammasome activation contributes to a wide variety of inflammatory diseases. Understanding the pathways that control NLRP3 activation will help develop strategies to treat these diseases. Here we identify WNK1 as a negative regulator of the NLRP3 inflammasome. Macrophages deficient in WNK1 protein or kinase activity have increased NLRP3 activation and pyroptosis compared with control macrophages. Mice with conditional knockout of WNK1 in macrophages have increased IL-1β production in response to NLRP3 stimulation compared with control mice. Mechanistically, WNK1 tempers NLRP3 activation by balancing intracellular Cl- and K+ concentrations during NLRP3 activation. Collectively, this work shows that the WNK1 pathway has a critical function in suppressing NLRP3 activation and suggests that pharmacological inhibition of this pathway to treat hypertension might have negative clinical implications.

WNK1 Enhances Migration and Invasion in Breast Cancer Models

Metastasis is the major cause of mortality in patients with breast cancer. Many signaling pathways have been linked to cancer invasiveness, but blockade of few protein components has succeeded in reducing metastasis. Thus, identification of proteins contributing to invasion that are manipulable by small molecules may be valuable in inhibiting spread of the disease. The protein kinase with no lysine (K) 1 (WNK1) has been suggested to induce migration of cells representing a range of cancer types. Analyses of mouse models and patient data have implicated WNK1 as one of a handful of genes uniquely linked to invasive breast cancer. Here, we present evidence that inhibition of WNK1 slows breast cancer metastasis. We show that depletion or inhibition of WNK1 reduces migration of several breast cancer cell lines in wound healing assays and decreases invasion in collagen matrices. Furthermore, WNK1 depletion suppresses expression of AXL, a tyrosine kinase implicated in metastasis. Finally, we demonstrate that WNK inhibition in mice attenuates tumor progression and metastatic burden. These data showing reduced migration, invasion, and metastasis upon WNK1 depletion in multiple breast cancer models suggest that WNK1 contributes to the metastatic phenotype, and that WNK1 inhibition may offer a therapeutic avenue for attenuating progression of invasive breast cancers.

Prognostic and Clinical Implications of WNK Lysine Deficient Protein Kinase 1 Expression in Patients With Hepatocellular Carcinoma

BACKGROUND/AIM

Hepatocellular carcinoma (HCC) is a particularly malignant form of cancer prevalent throughout the world; however, there is a pressing need for HCC biomarkers to facilitate prognosis and risk assessment.

PATIENTS AND METHODS

This paper reports on the potential prognostic value of WNK lysine deficient protein kinase 1 (WNK1) in cases of HCC. We analyzed the expression of WNK1 at the mRNA level using omics data from the UALCAN database. We then verified our findings through the immunohistochemical (IHC) staining of various human cancer tissue as well as 59 HCC samples paired with corresponding normal tissues. The prognostic value of mRNA or protein expression by WNK1 was evaluated using the Kaplan-Meier method.

RESULTS

Initial screening results revealed significantly higher WNK1 expression levels in HCC tissue compared to normal tissue. Verification using the paired HCC samples confirmed that the expression of WNK1 was indeed significantly higher in HCC tissue samples than in adjacent normal tissues. High WNK1 expression levels were significantly correlated with clinicopathological variables, including gender and histologic grade. Kaplan-Meier survival analysis revealed that high WNK1 expression levels were associated with poor HCC prognosis. Finally, univariate and multivariate analysis identified WNK1 as a prognostic factor for TNM stage in cases of HCC.

CONCLUSION

In summary, WNK1 is overexpressed at the mRNA and protein levels, and correlated with poor prognosis. Thus, WNK1 expression could potentially be used as a biomarker in HCC prognosis.

Control of Podocyte and Glomerular Capillary Wall Structure and Elasticity by WNK1 Kinase

Cytoskeletal structure and its regulation are essential for maintenance of the differentiated state of specific types of cells and their adaptation to physiologic and pathophysiologic conditions. Renal glomerular capillaries, composed of podocytes, endothelial cells, and the glomerular basement membrane, have distinct structural and biophysical properties and are the site of injury in many glomerular diseases. Calcineurin inhibitors, immunosuppressant drugs used for organ transplantation and auto-immune diseases, can protect podocytes and glomerular capillaries from injury by preserving podocyte cytoskeletal structure. These drugs cause complications including hypertension and hyperkalemia which are mediated by WNK (With No Lysine) kinases as well as vasculopathy with glomerulopathy. WNK kinases and their target kinases oxidative stress-responsive kinase 1 (OSR1) and SPS1-related proline/alanine-rich kinase (SPAK) have fundamental roles in angiogenesis and are activated by calcineurin inhibitors, but the actions of these agents on kidney vasculature, and glomerular capillaries are not fully understood. We investigated WNK1 expression in cultured podocytes and isolated mouse glomerular capillaries to determine if WNK1 contributes to calcineurin inhibitor-induced preservation of podocyte and glomerular structure. WNK1 and OSR1/SPAK are expressed in podocytes, and in a pattern similar to podocyte synaptopodin in glomerular capillaries. Calcineurin inhibitors increased active OSR1/SPAK in glomerular capillaries, the Young’s modulus (E) of glomeruli, and the F/G actin ratio, effects all blocked by WNK inhibition. In glomeruli, WNK inhibition caused reduced and irregular synaptopodin-staining, abnormal capillary and foot process structures, and increased deformability. In cultured podocytes, FK506 activated OSR1/SPAK, increased lamellipodia, accelerated cell migration, and promoted traction force. These actions of FK506 were reduced by depletion of WNK1. Collectively, these results demonstrate the importance of WNK1 in regulation of the podocyte actin cytoskeleton, biophysical properties of glomerular capillaries, and slit diaphragm structure, all of which are essential to normal kidney function.

WNK1-TAK1 signaling suppresses lipopolysaccharide-induced cytokine production and classical activation in macrophages

With-no-lysine kinase (WNK) plays important roles in regulating electrolyte homeostasis, cell signaling, survival, and proliferation. It has been recently demonstrated that WNK1, a member of the WNK family, modifies the function of immune cells. Here we report that in macrophages, WNK1 has suppressive effects on lipopolysaccharide (LPS)-induced inflammatory responses via TGFβ-activated kinase 1 (TAK1)-mediated activation of nuclear factor-kappa B (NF-κB) and mitogen-activated protein kinase (MAPK) signaling pathway. We found that WNK1 heterozygous (WNK1^+/-) mice produced excessive proinflammatory cytokines in an experimental LPS-induced sepsis model, and peritoneal macrophages isolated from WNK1^+/- mice produced higher levels of LPS-induced cytokines and NOS2 expression as canonical proinflammatory M1 macrophage markers. We confirmed that small hairpin RNA (shRNA)-mediated knockdown of WNK1 activated LPS-induced cytokine production and NOS2 expression in RAW 264.7 macrophages. Moreover, we demonstrated that WNK1 knockdown increased the nuclear translocation of NF-κB and activated the p38 and Jun N-terminal kinase (JNK) MAPK signaling pathway and that a TAK1 inhibitor diminished these effects of WNK1 knockdown. These results suggest that WNK1 acts as a physiologic immune modulator via interactions with TAK1. WNK1 may be a therapeutic target against the cytokine storm caused by sepsis.

WNK1 regulates uterine homeostasis and its ability to support pregnancy

WNK1 (with no lysine [K] kinase 1) is an atypical kinase protein ubiquitously expressed in humans and mice. A mutation in its encoding gene causes hypertension in humans, which is associated with abnormal ion homeostasis. WNK1 is critical for in vitro decidualization in human endometrial stromal cells, thereby demonstrating its importance in female reproduction. Using a mouse model, WNK1 was ablated in the female reproductive tract to define its in vivo role in uterine biology. Loss of WNK1 altered uterine morphology, causing endometrial epithelial hyperplasia, adenomyotic features, and a delay in embryo implantation, ultimately resulting in compromised fertility. Combining transcriptomic, proteomic, and interactomic analyses revealed a potentially novel regulatory pathway whereby WNK1 represses AKT phosphorylation through protein phosphatase 2A (PP2A) in endometrial cells from both humans and mice. We show that WNK1 interacted with PPP2R1A, the alpha isoform of the PP2A scaffold subunit. This maintained the levels of PP2A subunits and stabilized its activity, which then dephosphorylated AKT. Therefore, loss of WNK1 reduced PP2A activity, causing AKT hypersignaling. Using FOXO1 as a readout of AKT activity, we demonstrate that there was escalated FOXO1 phosphorylation and nuclear exclusion, leading to a disruption in the expression of genes that are crucial for embryo implantation.

Physiological Processes Modulated by the Chloride-Sensitive WNK-SPAK/OSR1 Kinase Signaling Pathway and the Cation-Coupled Chloride Cotransporters

The role of Cl- as an intracellular signaling ion has been increasingly recognized in recent years. One of the currently best described roles of Cl- in signaling is the modulation of the With-No-Lysine (K) (WNK) - STE20-Proline Alanine rich Kinase (SPAK)/Oxidative Stress Responsive Kinase 1 (OSR1) - Cation-Coupled Cl- Cotransporters (CCCs) cascade. Binding of a Cl- anion to the active site of WNK kinases directly modulates their activity, promoting their inhibition. WNK activation due to Cl- release from the binding site leads to phosphorylation and activation of SPAK/OSR1, which in turn phosphorylate the CCCs. Phosphorylation by WNKs-SPAK/OSR1 of the Na+-driven CCCs (mediating ions influx) promote their activation, whereas that of the K+-driven CCCs (mediating ions efflux) promote their inhibition. This results in net Cl- influx and feedback inhibition of WNK kinases. A wide variety of alterations to this pathway have been recognized as the cause of several human diseases, with manifestations in different systems. The understanding of WNK kinases as Cl- sensitive proteins has allowed us to better understand the mechanistic details of regulatory processes involved in diverse physiological phenomena that are reviewed here. These include cell volume regulation, potassium sensing and intracellular signaling in the renal distal convoluted tubule, and regulation of the neuronal response to the neurotransmitter GABA.

Critical role of WNK1 in MYC-dependent early mouse thymocyte development

WNK1, a kinase that controls kidney salt homeostasis, also regulates adhesion and migration in CD4+ T cells. Wnk1 is highly expressed in thymocytes, and since migration is important for thymocyte maturation, we investigated a role for WNK1 in mouse thymocyte development. We find that WNK1 is required for the transition of double negative (DN) thymocytes through the β-selection checkpoint and subsequent proliferation and differentiation into double positive (DP) thymocytes. Furthermore, we show that WNK1 negatively regulates LFA1-mediated adhesion and positively regulates CXCL12-induced migration in DN thymocytes. Despite this, migration defects of WNK1-deficient thymocytes do not account for the developmental arrest. Instead, we show that in DN thymocytes WNK1 transduces pre-TCR signals via OXSR1 and STK39 kinases, and the SLC12A2 ion co-transporter that are required for post-transcriptional upregulation of MYC and subsequent proliferation and differentiation into DP thymocytes. Thus, a pathway regulating ion homeostasis is a critical regulator of thymocyte development.

Role of the Cation-Chloride-Cotransporters in Cardiovascular Disease

The SLC12 family of cation-chloride-cotransporters (CCCs) is comprised of potassium chloride cotransporters (KCCs), which mediate Cl- extrusion and sodium-potassium chloride cotransporters (N[K]CCs), which mediate Cl- loading. The CCCs play vital roles in cell volume regulation and ion homeostasis. The functions of CCCs influence a variety of physiological processes, many of which overlap with the pathophysiology of cardiovascular disease. Although not all of the cotransporters have been linked to Mendelian genetic disorders, recent studies have provided new insights into their functional role in vascular and renal cells in addition to their contribution to cardiovascular diseases. Particularly, an imbalance in potassium levels promotes the pathogenesis of atherosclerosis and disturbances in sodium homeostasis are one of the causes of hypertension. Recent findings suggest hypothalamic signaling as a key signaling pathway in the pathophysiology of hypertension. In this review, we summarize and discuss the role of CCCs in cardiovascular disease with particular emphasis on knowledge gained in recent years on NKCCs and KCCs.

Flaming the fight against cancer cells: the role of microRNA-93

There have been attempts to develop novel anti-tumor drugs in cancer therapy. Although satisfying results have been observed at a consequence of application of chemotherapeutic agents, the cancer cells are capable of making resistance into these agents. This has forced scientists into genetic manipulation as genetic alterations are responsible for generation of a high number of cancer cells. MicroRNAs (miRs) are endogenous, short non-coding RNAs that affect target genes at the post-transcriptional level. Increasing evidence reveals the potential role of miRs in regulation of biological processes including angiogenesis, metabolism, cell proliferation, cell division, and cell differentiation. Abnormal expression of miRs is associated with development of a number of pathologic events, particularly cancer. MiR-93 plays a significant role in both physiological and pathological mechanisms. At the present review, we show how this miR dually affects the proliferation and invasion of cancer cells. Besides, we elucidate the oncogenesis or oncosuppressor function of miR-93.

WNK1 Kinase Stimulates Angiogenesis to Promote Tumor Growth and Metastasis

With-no-lysine (K)-1 (WNK1) is the founding member of family of four protein kinases with atypical placement of catalytic lysine that play important roles in regulating epithelial ion transport. Gain-of-function mutations of WNK1 and WNK4 cause a mendelian hypertension and hyperkalemic disease. WNK1 is ubiquitously expressed and essential for embryonic angiogenesis in mice. Increasing evidence indicates the role of WNK kinases in tumorigenesis at least partly by stimulating tumor cell proliferation. Here, we show that human hepatoma cells xenotransplanted into zebrafish produced high levels of vascular endothelial growth factor (VEGF) and WNK1, and induced expression of zebrafish wnk1. Knockdown of wnk1 in zebrafish decreased tumor-induced ectopic vessel formation and inhibited tumor proliferation. Inhibition of WNK1 or its downstream kinases OSR1 (oxidative stress responsive kinase 1)/SPAK (Ste20-related proline alanine rich kinase) using chemical inhibitors decreased ectopic vessel formation as well as proliferation of xenotransplanted hepatoma cells. The effect of WNK and OSR1 inhibitors is greater than that achieved by inhibitor of VEGF signaling cascade. These inhibitors also effectively inhibited tumorigenesis in two separate transgenic zebrafish models of intestinal and hepatocellular carcinomas. Endothelial-specific overexpression of wnk1 enhanced tumorigenesis in transgenic carcinogenic fish, supporting endothelial cell-autonomous effect of WNK1 in tumor promotion. Thus, WNK1 can promote tumorigenesis by multiple effects that include stimulating tumor angiogenesis. Inhibition of WNK1 may be a potent anti-cancer therapy.

WNK1-OSR1/SPAK KINASE CASCADE IS IMPORTANT FOR ANGIOGENESIS

WNK [with-no-lysine (K)] kinases are a family of four members of serine and threonine kinases that regulate renal Na+ and K+ transport. Mutations of WNK1 and WNK4 cause a hereditary hypertensive and hyperkalemic disease known as pseudohypoaldosteronism type II (PHA2). Unlike other WNK isoforms, WNK1 is ubiquitously expressed and regulates many other cellular processes outside the kidney. Oxidative stress response kinase (OSR1) and related STE 20/SPS1-related proline alanine-rich kinase (SPAK) are downstream kinases of WNK kinases. To examine the role of WNK kinase cascade in vivo, we generated global Wnk1-deleted mice and found that Wnk1-ablated mice die in utero from embryonic angiogenesis and cardiac developmental defects. Endothelial-specific Wnk1 deletion reveals that angiogenesis defect is due to WNK1 requirement in endothelium. We further showed that global and endothelial-deletion of Osr1 phenocopies Wnk1 deletion. Furthermore, expression of a catalytic constitutively active Osr1 transgene rescues angiogenesis defects and embryonic lethality of Wnk1-ablated mice. In zebrafish, Wnk1 knockdown causes similar angiogenesis defects to Vegf2 (Flk1) knockdown and that expression of WNK1 partially rescues Flk1 angiogenesis defects. The results indicate that WNK1 is downstream of VEGF signaling cascade. T-lymphocytes isolated from Wnk1-null mice exhibit migration defects. Inhibition of WNK1-OSR1 downstream target Na-K-2Cl cotransporter NKCC1 mimics migration defect of WNK1-deficient T-lymphocytes. Thus, WNK1-OSR1/SPAK cascade is important for angiogenesis. Regulation of ion homeostasis and cell volume may underlie the mechanism for WNK1 regulation of endothelial cell migration and angiogenesis.

Whole Blood Gene Expression Associated With Clinical Biological Age

Background

Biologic age may better reflect an individual's rate of aging than chronologic age.

Methods

We conducted a transcriptome-wide association study with biologic age estimated with clinical biomarkers, which included: systolic blood pressure, forced expiratory volume at 1 second (FEV1), total cholesterol, fasting glucose, C-reactive protein, and serum creatinine. We assessed the association between the difference between biologic age and chronologic age (∆age) and gene expression in whole blood measured using the Affymetrix Human Exon 1.0st Array.

Results

Our discovery sample included 2,163 participants from the Framingham Offspring cohort (mean age 67 ± 9 years, 55% women). A total of 481 genes were significantly associated with ∆age (p < 2.8 × 10-6). Among them, 415 genes were validated (p < .05/481 = 1.0 × 10-4) in 2,946 participants from the Framingham Third Generation cohort (mean age 46 ± 9 years, 53% women). Many of the significant genes were involved in the ubiquitin-mediated proteolysis pathway. The replication in 414 Rotterdam Study participants (mean age 59 ± 8, 52% women) found 104 of 415 validated genes reached nominal significance (p < .05).

Conclusion

We identified and validated 415 genes associated with ∆age in a community-based cohort. Future functional characterization of the biologic age-related gene network may identify targets to test for interventions to delay aging in older adults.

Smooth muscle-specific TMEM16A expression protects against angiotensin II-induced cerebrovascular remodeling via suppressing extracellular matrix deposition

Cerebrovascular remodeling is the leading factor for stroke and characterized by increased extracellular matrix deposition, migration and proliferation of vascular smooth muscle cells, and inhibition of their apoptosis. TMEM16A is an important component of Ca²⁺-activated Cl^- channels. Previously, we showed that downregulation of TMEM16A in the basilar artery was negatively correlated with cerebrovascular remodeling during hypertension. However, it is unclear whether TMEM16A participates in angiotensin II (Ang II)-induced vascular remodeling in mice that have TMEM16A gene modification. In this study, we generated a transgenic mouse that overexpresses TMEM16A specifically in vascular smooth muscle cells. We observed that vascular remodeling in the basilar artery during Ang II-induced hypertension was significantly suppressed upon vascular smooth muscle-specific overexpression of TMEM16A relative to control mice. Specifically, we observed a large reduction in the deposition of fibronectin and collagen I. The expression of matrix metalloproteinases (MMP-2, MMP-9, and MMP-14), and tissue inhibitors of metalloproteinases (TIMP-1 and TIMP-2) were upregulated in the basilar artery during Ang II-induced hypertension, but this was suppressed upon overexpression of TMEM16A in blood vessels. Furthermore, TMEM16A overexpression alleviated the overactivity of the canonical TGF-β1/Smad3, and non-canonical TGF-β1/ERK and JNK pathways in the basilar artery during Ang II-induced hypertension. These in vivo results were similar to the results derived in vitro with basilar artery smooth muscle cells stimulated by Ang II. Moreover, we observed that the inhibitory effect of TMEM16A on MMPs was mediated by decreasing the activation of WNK1, which is a Cl^--sensitive serine/threonine kinase. In conclusion, this study demonstrates that TMEM16A protects against cerebrovascular remodeling during hypertension by suppressing extracellular matrix deposition. We also showed that TMEM16A exerts this effect by reducing the expression of MMPs via inhibiting WNK1, and decreasing the subsequent activities of TGF-β1/Smad3, ERK, and JNK. Accordingly, our results suggest that TMEM16A may serve as a novel therapeutic target for vascular remodeling.

Endoplasmic reticulum and the microRNA environment in the cardiovascular system 1

Stress responses are important to human physiology and pathology, and the inability to adapt to cellular stress leads to cell death. To mitigate cellular stress and re-establish homeostasis, cells, including those in the cardiovascular system, activate stress coping response mechanisms. The endoplasmic reticulum, a component of the cellular reticular network in cardiac cells, mobilizes so-called endoplasmic reticulum stress coping responses, such as the unfolded protein response. MicroRNAs play an important part in the maintenance of cellular and tissue homeostasis, perform a central role in the biology of the cardiac myocyte, and are involved in pathological cardiac function and remodeling. In this paper, we review a link between endoplasmic reticulum homeostasis and microRNA with an emphasis on the impact on stress responses in the cardiovascular system.

WNK pathways in cancer signaling networks

Background

The with no lysine [K] (WNK) pathway consists of the structurally unique WNK kinases, their downstream target kinases, oxidative stress responsive (OSR)1 and SPS/Ste20-related proline-alanine-rich kinase (SPAK), and a multitude of OSR1/SPAK substrates including cation chloride cotransporters.

Main body

While the best known functions of the WNK pathway is regulation of ion transport across cell membranes, WNK pathway components have been implicated in numerous human diseases. The goal of our review is to draw attention to how this pathway and its components exert influence on the progression of cancer, specifically by detailing WNK signaling intersections with major cell communication networks and processes.

Conclusion

Here we describe how WNKs and associated proteins interact with and influence PI3K-AKT, TGF-β, and NF-κB signaling, as well as its unanticipated role in the regulation of angiogenesis.

WNK lysine deficient protein kinase 1 regulates human endometrial stromal cell decidualization, proliferation, and migration in part through mitogen-activated protein kinase 7

The differentiation of endometrial stromal cells into decidual cells, termed decidualization, is an integral step in the establishment of pregnancy. The mitogen-activated protein kinase homolog, WNK lysine deficient protein kinase 1 (WNK1), is activated downstream of epidermal growth factor receptor during decidualization. Primary human endometrial stromal cells (HESCs) were subjected to small interfering RNA knockdown of WNK1 followed by in vitro decidualization. This abrogated expression of the decidual marker genes, insulin like growth factor binding protein 1 (IGFBP1) and prolactin (PRL), and prevented adoption of decidual cell morphology. Analysis of the WNK1-dependent transcriptome by RNA-Seq demonstrated that WNK1 regulates the expression of 1858 genes during decidualization. Gene ontology and upstream regulator pathway analysis showed that WNK1 regulates cell migration, differentiation, and proliferation. WNK1 was required for many of the gene expression changes that drive decidualization, including the induction of the inflammatory cytokines, C-C motif chemokine ligand 8 (CCL8), interleukin 1 beta (IL1B), and interleukin 15 (IL15), and the repression of transforming growth factor-beta (TGF-beta) pathway genes, including early growth response 2 (EGR2), SMAD family member 3 (SMAD3), integrin subunit alpha 2 (ITGA2), integrin subunit alpha 4 (ITGA4), and integrin subunit beta 3 (ITGB3). In addition to abrogating decidualization, WNK1 knockdown decreased the migration and proliferation of HESCs. Furthermore, mitogen-activated protein kinase 7 (MAPK7), a known downstream target of WNK1, was activated during decidualization in a WNK1-dependent manner. Small interfering RNA knockdown of MAPK7 demonstrated that MAPK7 regulates a subset of WNK1-regulated genes and controls the migration and proliferation of HESCs. These results indicate that WNK1 and MAPK7 promote migration and proliferation during decidualization and regulate the expression of inflammatory cytokines and TGF-beta pathway genes in HESCs.

WNK1 regulates skeletal muscle cell hypertrophy by modulating the nuclear localization and transcriptional activity of FOXO4

With-no-lysine (K) (WNK) kinases, which are mutated in the inherited form of hypertension pseudohypoaldosteronism type II, are essential regulators of membrane ion transporters. Here, we report that WNK1 positively regulates skeletal muscle cell hypertrophy via mediating the function of the pro-longevity transcription factor forkhead box protein O4 (FOXO4) independent of the conventional WNK signaling pathway linking SPS/STE20-related proline-alanine–rich kinase (SPAK)/oxidative stress response kinase 1 (OSR1) to downstream effector ion transporters. Small interfering RNA (siRNA)-mediated silencing of WNK1, but not SPAK/OSR1 kinases, induced myotube atrophy and remarkable increases in the mRNA expression of the muscle atrophy ubiquitin ligases MAFbx and MuRF1 in C2C12 mouse skeletal muscle cells. WNK1 silencing also increased FOXO4 nuclear localization, and co-transfection of Foxo4-targeted siRNA completely reversed the myotube atrophy and upregulation of atrogene transcription induced by WNK1 silencing. We further illustrated that WNK1 protein abundance in skeletal muscle was increased by chronic voluntary wheel running exercise (hypertrophic stimulus) and markedly decreased by adenine-induced chronic kidney disease (atrophic stimulus) in mice. These findings suggest that WNK1 is involved in the physiological regulation of mammalian skeletal muscle hypertrophy and atrophy via interactions with FOXO4. The WNK1-FOXO4 axis may be a potential therapeutic target in human diseases causing sarcopenia.

Loss of Apela Peptide in Mice Causes Low Penetrance Embryonic Lethality and Defects in Early Mesodermal Derivatives

Apela (also known as Elabela, Ende, and Toddler) is a small signaling peptide that activates the G-protein-coupled receptor Aplnr to stimulate cell migration during zebrafish gastrulation. Here, using CRISPR/Cas9 to generate a null, reporter-expressing allele, we study the role of Apela in the developing mouse embryo. We found that loss of Apela results in low-penetrance cardiovascular defects that manifest after the onset of circulation. Three-dimensional micro-computed tomography revealed a higher penetrance of vascular remodeling defects, from which some mutants recover, and identified extraembryonic anomalies as the earliest morphological distinction in Apela mutant embryos. Transcriptomics at late gastrulation identified aberrant upregulation of erythroid and myeloid markers in mutant embryos prior to the appearance of physical malformations. Double-mutant analyses showed that loss of Apela signaling impacts early Aplnr-expressing mesodermal populations independently of the alternative ligand Apelin, leading to lethal cardiac defects in some Apela null embryos.

OSR1 regulates a subset of inward rectifier potassium channels via a binding motif variant

The with-no-lysine (K) (WNK) signaling pathway to STE20/SPS1-related proline- and alanine-rich kinase (SPAK) and oxidative stress-responsive 1 (OSR1) kinase is an important mediator of cell volume and ion transport. SPAK and OSR1 associate with upstream kinases WNK 1-4, substrates, and other proteins through their C-terminal domains which interact with linear R-F-x-V/I sequence motifs. In this study we find that SPAK and OSR1 also interact with similar affinity with a motif variant, R-x-F-x-V/I. Eight of 16 human inward rectifier K⁺ channels have an R-x-F-x-V motif. We demonstrate that two of these channels, Kir2.1 and Kir2.3, are activated by OSR1, while Kir4.1, which does not contain the motif, is not sensitive to changes in OSR1 or WNK activity. Mutation of the motif prevents activation of Kir2.3 by OSR1. Both siRNA knockdown of OSR1 and chemical inhibition of WNK activity disrupt NaCl-induced plasma membrane localization of Kir2.3. Our results suggest a mechanism by which WNK-OSR1 enhance Kir2.1 and Kir2.3 channel activity by increasing their plasma membrane localization. Regulation of members of the inward rectifier K⁺ channel family adds functional and mechanistic insight into the physiological impact of the WNK pathway.

Essentiality of Regulator of G Protein Signaling 6 and Oxidized Ca2+/Calmodulin-Dependent Protein Kinase II in Notch Signaling and Cardiovascular Development

Background

Congenital heart defects are the most common birth defects worldwide. Although defective Notch signaling is the major cause of mouse embryonic death from cardiovascular defects, how Notch signaling is regulated during embryonic vasculogenesis and heart development is poorly understood.

Methods and Results

Regulator of G protein signaling 6 (RGS6)^−/−/Ca²⁺/calmodulin‐dependent protein kinase II (CaMKII)^VV double mutant mice were developed by crossing RGS6^−/− mice with mice expressing an oxidation‐resistant CaMKIIδ (CaMKII^VV), and the resulting embryonic defects/lethality were investigated using E7.5 to E15.5 embryos. While loss of either RGS6 or oxidized CaMKIIδ does not alter embryogenesis, their combined loss causes defective Notch signaling, severe cardiovascular defects, and embryonic lethality (≈E10.5–11.5). Embryos lacking RGS6 and expressing oxidation‐resistant CaMKIIδ exhibit reduced myocardial wall thickness, abnormal trabeculation, and arterial specification defects. Double mutants show vascular remodeling defects, including reduced neurovascularization, delayed neural tube maturation, and small dorsal aortae. These striking cardiovascular defects were accompanied by placental and yolk sac defects in angiogenesis, hematopoiesis, and vascular remodeling similar to what is seen with defective Notch1 signaling. Double mutant hearts, embryos, and yolk sacs exhibit profound downregulation of Notch1, Jagged 1, and Notch downstream target genes Hey1, Hey2, and Hey1L as well as impaired Notch1 signaling in embryos/hearts.

Conclusions

RGS6 and oxidized CaMKIIδ together function as novel critical upstream modulators of Notch signaling required for normal cardiovascular development and embryo survival. Their combined need indicates that they function in parallel pathways needed for Notch1 signaling in yolk sac, placenta and embryos. Thus, dysregulated embryonic RGS6 expression and oxidative activation of CaMKII may potentially contribute to congenital heart defects.

Emerging Targets of Diuretic Therapy

Diuretics are commonly prescribed for treatment in patients with hypertension, edema, or heart failure. Studies on hypertensive and salt-losing disorders and on urea transporters have contributed to better understanding of mechanisms of renal salt and water reabsorption and their regulation. Proteins involved in the regulatory pathways are emerging targets for diuretic and aquaretic therapy. Integrative high-throughput screening, protein structure analysis, and chemical modification have identified promising agents for preclinical testing in animals. These include WNK-SPAK inhibitors, ClC-K channel antagonists, ROMK channel antagonists, and pendrin and urea transporter inhibitors. We discuss the potential advantages and side effects of these potential diuretics.