Leukotactin-1-induced ERK activation is mediated via Gi/Go protein/PLC/PKC delta/Ras cascades in HOS cells

Enantioselective pharmacodynamics of propranolol in HUVEC cells: a study using chiral 2D gel electrophoresis and mass spectrometry

Propranolol (PRO), a nonselective β-adrenergic receptor (β-AR) antagonist, has two enantiomers, R(+)-PRO and S(-)-PRO, which have diverse biological effects. For example, S(-)-PRO blocks the β-receptor ~100 times more strongly than R(+)-PRO. However, the signaling pathway that causes this difference remains unclear. This pathway may affect the expression of numerous proteins, some of which play key roles during the drug action process. Therefore, we treated human umbilical vein endothelial cells (HUVECs) with R(+)-PRO and S(-)-PRO in order to identify differentially expressed proteins and to determine their functions in the drug action process. Of the 22 differentially expressed protein spots investigated, 14 demonstrated higher expression levels in the R(+)-PRO-treated cells, while 8 demonstrated lower expression levels in the same cells. Mass spectrometry identified 10 of the differentially expressed proteins: 4 signaling molecules, 2 metabolic enzymes, 3 heat shock proteins and 1 cytoskeleton protein. Our results suggest that these differentially expressed proteins, particularly guanine nucleotide-binding protein subunit β-2-like 1 (GBLP), are the key biomacromolecules underlying the mechanism by which PRO enantiomers induce stereoselective cellular responses. The results aid in clarifying the role of PRO in the treatment of arrhythmia and angina.

CCR1 as a target for multiple myeloma

INTRODUCTION

By directing cell trafficking, differentiation and growth, chemokines modulate the immune response and are involved in the pathogenesis of autoimmune diseases and cancers, including multiple myeloma (MM). MM, the second most common hematological malignancy in the US, is characterized by disordered plasma cell growth within the bone marrow microenvironment. CCL3 and its receptors, CCR1 in particular, play a central role in the pathogenesis of MM and MM-induced osteolytic bone disease.

AREAS COVERED

This review describes the functional role of CCR1 in MM and the preclinical results observed with CCR1 antagonists. CCL3 and CCR1 stimulate tumor growth, both directly and indirectly, via upregulation of cell adhesion and cytokine secretion. In addition, they modulate the osteoclast/osteoblast balance, by inducing osteoclast differentiation and inhibiting osteoblast function. Targeting either ligand or receptor reverses these effects, leading to in vivo tumor burden control and prevention of osteolysis, as confirmed in both murine and humanized mouse models.

EXPERT OPINION

These promising data set the stage for clinical trials to assess the effects of CCR1 inhibitors in MM. The success of these studies depends on the development of novel antagonists with improved chemical/physical properties and careful selection of the patient population who may benefit the most from these agents.

Leukotactin-1/CCL15 induces cell migration and differentiation of human eosinophilic leukemia EoL-1 cells through PKCdelta activation

Leukotactin-1 (Lkn-1)/CCL15 is a CC chemokine that binds to the CCR1 and CCR3. Lkn-1 functions as an essential factor in the migration of monocytes, lymphocytes, and neutrophils. Although eosinophils express both receptors, the role of Lkn-1 in immature eosinophils remains to be elucidated. In this present study, we investigated the contribution of the CCR1-binding chemokines to chemotactic activity and in the differentiation in the human eosinophilic leukemia cell line EoL-1. Lkn-1 induced the stronger migration of EoL-1 cells than other CCR1-binding chemokines such as RANTES/CCL5, MIP-1alpha/CCL3 and HCC-4/CCL16. Lkn-1-induced chemotaxis was inhibited by pertussis toxin, an inhibitor of G(i)/G(o) protein; U73122, an inhibitor of phospholipase C and rottlerin, an inhibitor of protein kinase C delta (PKCdelta). Lkn-1 increased PKCdelta activity, which was partially blocked by the pertussis toxin and U73122. Lkn-1 enhanced the butyric acid-induced differentiation via PKCdelta after binding to the increased CCR1 because Lkn-1 caused EoL-1 cells to change morphologically into mature eosinophil-like cells. Likewise, Lkn-1 increased the expression of both eosinophil peroxidase (EPO) and the major basic protein (MBP). PKCdelta activation due to Lkn-1 is involved in migration, as well as the butyric acid-induced differentiation. This finding contributes to an understanding of CC chemokines in eosinophil biology and to the development of novel therapies for the treatment of eosinophilic disorders. This study suggests the pivotal roles of Lkn-1 in the regulation of the movement and development of eosinophils.

CCL23 up-regulates expression of KDR/Flk-1 and potentiates VEGF-induced proliferation and migration of human endothelial cells

CCL23 is a CC chemokine and exerts its biological activities on endothelial cells as well as on immune cells through CCR1. We investigated the potential effect of CCL23 on expression of KDR/Flk-1 receptor in endothelial cells. PCR, confocal microscope and Western blot analysis revealed that CCL23 up-regulated KDR/Flk-1 mRNA and protein levels in endothelial cells. A reporter assay indicated that CCL23-induced KDR/Flk-1 expression primarily occurred at the transcriptional level. In addition, CCL23 stimulated phosphorylation of SAPK/JNK, and an inhibitor of SAPK/JNK blocks the CCL23-induced KDR/Flk-1 expression. Furthermore, VEGF-induced ERK phosphorylation was stimulated by CCL23. Finally, CCL23 promoted VEGF-induced endothelial proliferation and migration, which were correlated with the maximal stimulation of KDR/Flk-1 expression by CCL23. Taken together, these findings suggest that CCL23 results in up-regulation of KDR/flk-1 receptor gene transcription and protein expression and that KDR/Flk-1 up-regulation induced by CCL23 may contribute to potentiation of VEGF action in angiogenesis.

Role of human LZIP in differential activation of the NF-kappaB pathway that is induced by CCR1-dependent chemokines

Human leucine zipper protein (LZIP) associates with CC chemokine receptor 1 (CCR1) and this protein-protein interaction should play an important role in leukocyte cell mobility. LZIP is known to regulate leukotactin-1 (Lkn-1)-dependent cell migration without affecting the chemotactic activities of other CC chemokines that bind to CCR1. Since Lkn-1 is engaged in the transcriptional activation of nuclear factor kappaB (NF-kappaB) and subsequent activation of the chemoattractant ability of leukocytes, we investigated the regulatory role of LZIP in the NF-kappaB pathway that is induced by CCR1-dependent chemokines. LZIP increased NF-kappaB-dependent luciferase activity in response to Lkn-1 in HOS/CCR1 cells and THP-1 cells. However, the NF-kappaB-dependent luciferase activities induced by other CCR1-dependent chemokines were not affected by LZIP overexpression. LZIP also increased Lkn-1-induced chemotactic activity through activation of the NF-kappaB pathway, whereas LZIP did not affect either the transactivation of NF-kappaB or the chemotactic activities induced by other CCR1-dependent chemokines. Western blot analysis showed that LZIP increased the degradation of IkappaBalpha induced by Lkn-1 but not by other CCR1-dependent chemokines. Results from electrophoretic mobility shift assay (EMSA) showed that LZIP enhanced the Lkn-1-induced DNA-binding activity of NF-kappaB. These data indicate that LZIP functions as a positive regulator in the NF-kappaB activation pathway that is triggered by Lkn-1 without affecting the transcriptional activation of NF-kappaB induced by other CCR1-dependent chemokines.

YWK-II protein as a novel Go-coupled receptor for Müllerian inhibiting substance in cell survival

Müllerian inhibiting substance (MIS) has recently been implicated in multiple cellular functions including promotion of cell survival, but the receptor(s) and signaling pathways involved remain elusive. We have investigated the possibility of YWK-II protein, previously shown to interact physically with MIS and Go protein, being a receptor mediating the cell survival effect of MIS. In YWK-II-overexpressing CHO cells, MIS activates the Go-coupled ERK1/2 signaling pathway and promotes cell survival with altered levels of p53 and caspase-3. YWK-II antibody is found to interfere with the ability of MIS to promote viability of mouse sperm and affect MIS-activated ERK1/2 phosphorylation. In vivo studies involving injection of YWK-II antibody into the seminiferous tubule of the mouse testis, where MIS is known to be produced, show significant reduction in the sperm count with accumulation of p53 and cleaved caspase-3 in testicular nuclei. Taken together, the present study has demonstrated a new Go-coupled receptor for MIS in mediating ERK1/2 activation leading to anti-apoptotic activity or cell survival.

Regulation of human LZIP expression by NF-kappaB and its involvement in monocyte cell migration induced by Lkn-1

Human LZIP is a transcription factor that is involved in leukocyte cell mobility. Expression of LZIP is known to differentially regulate monocyte cell migration induced by CCR1-dependent chemokines. However, its transcriptional regulation has not been characterized. Our results indicate that Lkn-1 induces LZIP expression in a time- and dose-dependent manner, and the induction of LZIP shows an immediate early response to Lkn-1. We identified and cloned approximately 1.4 kb of the LZIP promoter from a human genomic DNA. To identify regulatory elements controlling restricted expression of LZIP, deletion mutants were constructed from the 1469-bp LZIP promoter region (-1219/+251) linked to the luciferase reporter gene. Maximal promoter activity was contained within 613 bp from the tentative transcription initiation site and was sharply reduced in a truncated construct (-338/+251). This promoter sequence contained consensus NF-kappaB- and Sp-1-binding sites. Results from an inhibitor assay showed that NF-kappaB is involved in Lkn-1-induced LZIP expression, but Sp-1 is not. We also demonstrated that NF-kappaB binds to the LZIP promoter and that the binding is specific, as revealed by an electrophoretic mobility shift assay and a mutation analysis. Chemotaxis analysis showed that LZIP expression because of the NF-kappaB subfamily is specifically involved in Lkn-1-induced chemotaxis. Our findings suggest that transcription factor NF-kappaB plays an important role in regulation of LZIP expression, and LZIP expression regulates the monocyte cell migration induced by Lkn-1.

Adenoviral gene transfer of a mutant surfactant enzyme ameliorates pseudomonas-induced lung injury

Surfactant deficiency is an important contributor to the acute respiratory distress syndrome, a disorder that commonly occurs after bacterial sepsis. CTP:phosphocholine cytidylyltransferase (CCTalpha) is the rate-limiting enzyme required for the biosynthesis of dipalmitoylphosphatidylcholine (DPPC), the major phospholipid of surfactant. In this study, a cDNA encoding a novel, calpain-resistant mutant CCTalpha enzyme was delivered intratracheally in mice using a replication-deficient adenovirus 5 CTP:phosphocholine cytidylyltransferase construct (Ad5-CCT(Penta)) in models of bacterial sepsis. Ad5-CCT(Penta) gene transfer produced high-level CCTalpha gene expression, increased alveolar surfactant (DPPC) levels and improved lung surface tension and pressure-volume relationships relative to control mice. Pseudomonas aeruginosa (PA103) decreased DPPC synthesis, in part, via calpain-mediated degradation of CCTalpha. Deleterious effects of Pseudomonas on surfactant were lessened after infection with a mutant strain lacking the type III exotoxin, Exo U. Replication-deficient adenovirus 5 CTP:phosphocholine cytidylyltransferase gene delivery improved lung biophysical properties by optimizing surface activity in this Pseudomonas model of proteinase-mediated lung injury. The studies are the first demonstration of in vivo gene transfer of a lipogenic enzyme resulting in improved lung mechanics. The studies suggest that augmentation of DPPC synthesis via gene delivery of CCTalpha can attenuate impaired lung function in surfactant-deficient states such as bacterial sepsis.

Differential CCR1-mediated chemotaxis signaling induced by human CC chemokine HCC-4/CCL16 in HOS cells

Human CC chemokine-4 (HCC-4)/CCL16 is a chemoattractant for monocytes and lymphocytes. Although HCC-4 binds to multiple CC chemokine receptors, the receptor-mediated signal transduction pathway induced by HCC-4 has not been characterized. Human osteogenic sarcoma cells stably expressing CCR1 were used to investigate HCC-4-mediated chemotaxis signaling events via CCR1. The chemotactic activity of HCC-4 as well as those of other CCR1-dependent chemokines including MIP-1alpha/CCL3, RANTES/CCL5, and Lkn-1/CCL15 was inhibited by the treatment of pertussis toxin, an inhibitor of Gi/Go protein, U73122, an inhibitor of phospholipase C (PLC), and rottlerin, a specific inhibitor of protein kinase Cdelta (PKCdelta). These results indicate that HCC-4-induced chemotaxis signaling is mediated through Gi/Go protein, PLC, and PKCdelta. SB202190, an inhibitor of p38 mitogen activated protein kinase, only blocked the chemotactic activity of HCC-4, but not those of other CCR1-dependent chemokines. SB202190 inhibited HCC-4-induced chemotaxis in a dose-dependent manner (P < 0.01). HCC-4 induces p38 activation in both a time and dose-dependent manner. However, such p38 activation was not induced by other CCR1-dependent chemokines. To further investigate the differential effect of HCC-4, the Ca2+ mobilization was examined. HCC-4 induced no intracellular Ca2+ flux in contrast to other CCR1-dependent chemokines. These results indicate that HCC-4 transduces signals differently from other CCR1-dependent chemokines and may play different roles in the immune response.

Oxysterols inhibit phosphatidylcholine synthesis via ERK docking and phosphorylation of CTP:phosphocholine cytidylyltransferase

Surfactant deficiency contributes to acute lung injury and may result from the elaboration of bioactive lipids such as oxysterols. We observed that the oxysterol 22-hydroxycholesterol (22-HC) in combination with its obligate partner, 9-cis-retinoic acid (9-cis-RA), decreased surfactant phosphatidylcholine (PtdCho) synthesis by increasing phosphorylation of the regulatory enzyme CTP:phosphocholine cytidylyltransferase-alpha (CCTalpha). Phosphorylation of CCTalpha decreased its activity. 22-HC/9-cis-RA inhibition of PtdCho synthesis was blocked by PD98059 or dominant-negative ERK (p42 kinase). Overexpression of constitutively active MEK1, the kinase upstream of p42 kinase, increased CCTalpha phosphorylation. Expression of truncated CCTalpha mutants lacking proline-directed sites within the C-terminal phosphorylation domain partially blocked oxysterol-mediated inhibition of PtdCho synthesis. Mutagenesis of Ser315 within CCTalpha was both required and sufficient to confer significant resistance to 22-HC/9-cis-RA inhibition of PtdCho synthesis. A novel putative ERK-docking domain N-terminal to this phosphoacceptor site was mapped within the CCTalpha membrane-binding domain (residues 287-300). The results are the first demonstration of a physiologically relevant phosphorylation site and docking domain within CCTalpha that serve as targets for ERKs, resulting in inhibition of surfactant synthesis.

PLP2/A4 interacts with CCR1 and stimulates migration of CCR1-expressing HOS cells

Multiple CC chemokines bind to CCR1, which plays important roles in immune and inflammatory responses. To search for proteins involved in the CCR1 signaling pathway, we screened a yeast two-hybrid library using the cytoplasmic tail of CCR1 as the bait. One of the positive clones contained an open reading frame of 456bp, of which the nucleotide sequence was identical to that of proteolipid protein 2 (PLP2), also known as protein A4. Mammalian two-hybrid and coimmunoprecipitation analyses demonstrated the association of PLP2/A4 with CCR1. Indirect immunofluorescence analysis revealed that PLP2/A4 was predominantly located in plasma membrane and colocalized with CCR1 in transfected human HEK293 cells. In addition, focal staining of CCR1 appeared on the periphery of the membrane upon short exposure to Leukotactin-1(Lkn-1)/CCL15, a CCR1 agonist, and was costained with PLP2/A4 on the focal regions. PLP2/A4 mRNAs were detected in various cells such as U-937, HL-60, HEK293, and HOS cells. Overexpression of PLP2/A4 stimulated a twofold increase in the agonist-induced migration of HOS/CCR1 cells, implicating a functional role for PLP2/A4 in the chemotactic processes via CCR1.