Multiple protein kinases determine the phosphorylated state of the small heat shock protein, HSP27, in SH-SY5Y neuroblastoma cells

Phosphoproteomic analysis sheds light on intracellular signaling cascades triggered by Formyl-Peptide Receptor 2

Formyl peptide receptors (FPRs) belong to the family of seven transmembrane Gi-protein coupled receptors (GPCR). FPR2 is considered the most promiscuous member of this family since it recognizes a wide variety of ligands. It plays a crucial role in several physio-pathological processes and different studies highlighted the correlation between its expression and the higher propensity to invasion and metastasis of some cancers. FPR2 stimulation by its synthetic agonist WKYMVm triggers multiple phosphorylations of intracellular signaling molecules, such as ERKs, PKC, PKB, p38MAPK, PI3K, PLC, and of non-signaling proteins, such as p47^phox and p67^phox which are involved in NADPH oxidase-dependent ROS generation. Biological effects of FPR2 stimulation include intracellular Ca²⁺ mobilization, cellular proliferation and migration, and wound healing. A systematic analysis of the phosphoproteome in FPR2-stimulated cells has not been yet reported. Herein, we describe a large-scale phosphoproteomic study in WKYMVm-stimulated CaLu-6 cells. By using high resolution MS/MS we identified 290 differentially phosphorylated proteins and 53 unique phosphopeptides mapping on 40 proteins. Phosphorylations on five selected phospho-proteins were further validated by western blotting, confirming their dependence on FPR2 stimulation. Interconnection between some of the signalling readout identified was also evaluated. Furthermore, we show that FPR2 stimulation with two anti-inflammatory agonists induces the phosphorylation of selected differentially phosphorylated proteins, suggesting their role in the resolution of inflammation. These data provide a promising resource for further studies on new signaling networks triggered by FPR2 and on novel molecular drug targets for human diseases.

Treatment of human neuroblastoma cell line SH-SY5Y with HSP27 siRNA tagged-exosomes decreased differentiation rate into mature neurons

Heat shock proteins (HSPs) participate in the regulation of different cell activities in response to stimuli. By applying different strategies, the modulation of heat shock proteins is at the center of attention. Conventional delivery approaches are not fully encouraged due to cytotoxicity and immunogenicity issues. Exosomes are touted as bio-shuttles for delivery of distinct biomolecules inside the cells. Here, we aimed to HSP27 small interfering RNA (siRNA)-tagged exosomes for the inhibition of Hsp27 in human neuroblastoma cell line SH-SY5Y and explored differentiation into neuron-like cells. Exosomes were isolated, characterized by scanning electron microscope (SEM) and CD63 then enriched with siRNA against Hsp27. Neuroblastoma cells were incubated with exosomes carrying siRNA for 48 hr. Exosome uptake was monitored by immunofluorescence assay. The cell viability and proliferation were analyzed using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide and bromodeoxyuridine/5-bromo-2'-deoxyuridine incorporation assays. The ability of cells to form colonies was evaluated by clonogenic assay. The cell potential to express NeuN, a mature neuron factor, was studied by flow cytometry analysis. SEM showed the nano-sized particles and a high level of CD63 after enrichment. Immunofluorescence imaging revealed an appropriate transfection rate in cell exposed to Hsp27 siRNA tagged exosomes. The cell viability and proliferation were reduced compared to cells received nude exosomes ( p < 0.05). Clonogenic activity of cells was diminished by the inhibition of Hsp27. Flow cytometry analysis revealed that the inhibition of Hsp27 prohibited NeuN content, showing the maturation of SH-SY5Y cells to mature cells compared to control. These data confirmed that exosomes could be used as appropriate bio-shuttles for the inhibition of Hsp27-aborted cell differentiation toward mature neuron.

M3 receptor is involved in the effect of penehyclidine hydrochloride reduced endothelial injury in LPS-stimulated human pulmonary microvascular endothelial cell

LPS has been recently shown to induce muscarinic acetylcholine 3 receptor (M₃ receptor) expression and penehyclidine hydrochloride (PHC) is an anticholinergic drug which could block the expression of M₃ receptor. PHC has been demonstrated to perform protective effect on cell injury. This study is to investigate whether the effect of PHC on microvascular endothelial injury is related to its inhibition of M₃ receptor or not. HPMVECs were treated with specific M₃ receptor shRNA or PBS, and randomly divided into LPS group (A group), LPS+PHC group (B group), LPS + M₃ shRNA group (C group) and LPS + PHC + M₃ shRNA group (D group). Cells were collected at 60 min after LPS treatment to measure levels of LDH, endothelial permeability, TNF-α and IL-6 levels, NF-κB p65 activation, I-κB protein expression, p38MAPK, and ERK1/2 activations as well as M₃ mRNA expression. PHC could decrease LDH levels, cell permeability, TNF-α and IL-6 levels, p38 MAPK, ERK1/2, NF-κB p65 activations and M₃ mRNA expressions compared with LPS group. When M₃ receptor was silence, the changes of these indices were much more obvious. These findings suggest that M₃ receptor plays an important role in LPS-induced pulmonary microvascular endothelial injury, which is regulated through NF-κB p65 and MAPK activation. And knockout of M₃ receptor could attenuate LPS-induced pulmonary microvascular endothelial injury. Regulative effects of PHC on pulmonary microvascular permeability and NF-κB p65 as well as MAPK activations are including but not limited to inhibition of M₃ receptor.

Mitogen-activated protein kinases regulate expression of neuronal nitric oxide synthase and neurite outgrowth via non-classical retinoic acid receptor signaling in human neuroblastoma SH-SY5Y cells

We have previously shown that retinoic acid receptor (RAR) stimulation by an agonist Am80 recruits nitric oxide-dependent signaling via increased expression of neuronal nitric oxide synthase (nNOS) in rat midbrain slice cultures. Using neuroblastoma SH-SY5Y cells, here we investigated the mechanisms of RAR-induced nNOS expression, together with relationship between nNOS expression and neurite outgrowth. Am80 promoted neurite outgrowth, which was attenuated by inhibitors of phosphoinositide 3-kinase (PI3K; LY294002), c-Jun N-terminal kinase (JNK; SP600125) and p38 mitogen-activated protein kinase (p38 MAPK; SB203580). A selective nNOS inhibitor 3-bromo-nitroindazole also suppressed Am80-induced neurite outgrowth. Am80-induced increase in nNOS protein expression was attenuated by LY294002, SP600125 and SB203580, whereas increase in nNOS mRNA expression was attenuated only by LY294002. Am80-induced activation of JNK and p38 MAPK was blocked by LY294002, suggesting that these kinases acted downstream of PI3K. We also confirmed that DAX1, a nuclear receptor reported to regulate nNOS expression, was up-regulated in response to Am80. siRNA-mediated knockdown of DAX1 abrogated Am80-induced nNOS expression and neurite outgrowth. These results reveal for the first time that nNOS expression is crucial for RAR-mediated neurite outgrowth, and that non-genomic signaling such as JNK and p38 MAPK is involved in RAR-mediated nNOS expression.

Immediate and transient phosphorylation of the heat shock protein 27 initiates chemoresistance in prostate cancer cells

Drug resistance minimizes the effects of prostate cancer (PC) chemotherapy with docetaxel and is generally considered to be associated with the expression of heat shock protein (HSP) 27 including various cytoprotective pathways. In the present study, we investigated the effects of HSP27 phosphorylation on PC cell growth underlying docetaxel treatment. Cell counting revealed significantly reduced cell growth during docetaxel treatment as a result of both activation of mitogen-activated protein kinase p38 (MAPK p38) and protein kinase D1 (PKD1), and, most importantly, the overexpression of the phosphorylation-mimicking mutant HSP27-3D. Further analysis revealed a docetaxel-dependent induction of HSP27 accompanied by an initial phosphorylation and rapid dephosphorylation of the protein. Based on the data, we can conclude that phosphorylation of HSP27 protein is a crucial mechanism in the initiation of chemoresistance in PC. Moreover, the results indicate a key impact of HSP27 on viability and proliferation of PC cells underlying anticancer therapy. The protective function depends on the initial phosphorylation status of HSP27 and represents a putative co-therapeutic target to prevent chemoresistance during docetaxel therapy.

Global changes in the rat heart proteome induced by prolonged morphine treatment and withdrawal

Morphine belongs among the most commonly used opioids in medical practice due to its strong analgesic effects. However, sustained administration of morphine leads to the development of tolerance and dependence and may cause long-lasting alterations in nervous tissue. Although proteomic approaches enabled to reveal changes in multiple gene expression in the brain as a consequence of morphine treatment, there is lack of information about the effect of this drug on heart tissue. Here we studied the effect of 10-day morphine exposure and subsequent drug withdrawal (3 or 6 days) on the rat heart proteome. Using the iTRAQ technique, we identified 541 proteins in the cytosol, 595 proteins in the plasma membrane-enriched fraction and 538 proteins in the mitochondria-enriched fraction derived from the left ventricles. Altogether, the expression levels of 237 proteins were altered by morphine treatment or withdrawal. The majority of changes (58 proteins) occurred in the cytosol after a 3-day abstinence period. Significant alterations were found in the expression of heat shock proteins (HSP27, α-B crystallin, HSP70, HSP10 and HSP60), whose levels were markedly up-regulated after morphine treatment or withdrawal. Besides that morphine exposure up-regulated MAPK p38 (isoform CRA_b) which is a well-known up-stream mediator of phosphorylation and activation of HSP27 and α-B crystallin. Whereas there were no alterations in the levels of proteins involved in oxidative stress, several changes were determined in the levels of pro- and anti-apoptotic proteins. These data provide a complex view on quantitative changes in the cardiac proteome induced by morphine treatment or withdrawal and demonstrate great sensitivity of this organ to morphine.

Phosphorylation of HSP27 by protein kinase D is essential for mediating neuroprotection against ischemic neuronal injury

Heat shock protein 27 (HSP27) (or HSPB1) exerts cytoprotection against many cellular insults, including cerebral ischemia. We previously identified apoptosis signal-regulating kinase 1 (ASK1) as a critical downstream target of HSP27 conferring the neuroprotective effects of HSP27 against neuronal ischemia. However, the function of HSP27 is highly influenced by posttranslational modification, with differential cellular effects based on phosphorylation at specific serine residues. The role of phosphorylation in neuronal ischemic neuroprotection is currently unknown. We have created transgenic mice and viral vectors containing HSP27 mutated at three critical serine residues (Ser15, Ser78, and Ser82) to either alanine (HSP27-A, nonphosphorylatable) or aspartate (HSP27-D, phosphomimetic) residues. Under both in vitro and in vivo neuronal ischemic settings, overexpression of wild-type HSP27 (HSP27) and HSP27-D, but not HSP27-A, was neuroprotective and inhibited downstream ASK1 signaling pathways. Consistently, overexpressed HSP27 was phosphorylated by endogenous mechanisms when neurons were under ischemic stress, and single-point mutations identified Ser15 and Ser82 as critical for neuroprotection. Using a panel of inhibitors and gene knockdown approaches, we identified the upstream kinase protein kinase D (PKD) as the primary kinase targeting HSP27 directly for phosphorylation. PKD and HSP27 coimmunoprecipitated, and inhibition or knockdown of PKD abrogated the neuroprotective effects of HSP27 as well as the interaction with and inhibition of ASK1 signaling. Together, these data demonstrate that HSP27 requires PKD-mediated phosphorylation for its suppression of ASK1 cell death signaling and neuroprotection against ischemic injury.