Protein kinase D is implicated in the reversible commitment to differentiation in primary cultures of mouse keratinocytes

PKCμ promotes keratinocyte cell migration through Cx43 phosphorylation-mediated suppression of intercellular communication

Downregulation of intercellular communication through suppression of gap junctional conductance is necessary during wound healing. Connexin 43 (Cx43), a prominent gap junction protein in skin, is downregulated following wounding to restrict communication between keratinocytes. Previous studies found that PKCμ, a novel PKC isozyme, regulates efficient cutaneous wound healing. However, the molecular mechanism by which PKCμ regulates wound healing remains unknown. We have identified that PKCμ suppresses intercellular communication and enhances cell migration in an in vitro wound healing model by regulating Cx43 containing gap junctions. PKCμ can directly interact with and phosphorylate Cx43 at S368, which leads to Cx43 internalization and downregulation. Finally, utilizing phosphomimetic and non-phosphorylatable S368 substitutions and gap junction inhibitors, we confirmed that PKCμ regulates intercellular communication and in vitro wound healing by controlling Cx43-S368 phosphorylation. These results define PKCμ as a critical regulator of Cx43 phosphorylation to control cell migration and wound healing in keratinocytes.

Fabrication of poly (lactic-co-glycolic acid)/gelatin electro spun nanofiber patch containing CaCO3/SiO2 nanocomposite and quercetin for accelerated diabetic wound healing

An open wound or sore on the bottom of the foot caused by diabetes is known as a diabetic foot ulcer. Preventive measures are essential, including consistent foot care and glycemic management. The dangers associated with diabetic foot ulcers can be reduced via early identification and timely treatment. The risk of foot ulcers and limb amputation increases with age and duration of diabetes. Quercetin contains anti-inflammatory and antioxidant properties. Furthermore, the calcium carbonate/silica (CaCO3/SiO2) nanocomposite has a good anti-inflammatory property due to the presence of calcium, which will aid in wound healing. As a result, combining quercetin (plant based anti-inflammatory drug) and CaCO3/SiO2 nanocomposite will boost the wound healing rate. We have synthesized CaCO3/SiO2 nanocomposite in sol-gel method and characterized using XRD, FTIR and TEM. Cell line tests and the MTT assay revealed that the PLGA/gelatin/CaCO3/SiO2/quercetin patch enhanced the proliferation of cells. Its anti-bacterial efficacy against four major bacterial strains often found in wound locations, as well as its water retention, make it an ideal material for diabetic wound healing. In-vivo trials confirms the enhanced diabetic wound healing potential of the patch.

A protein kinase D inhibitor suppresses AKT on T cells and antagonizes cancer immunotherapy by anti-PD-1

Antibodies that block the interaction between PD-1 and PD-1 ligands (anti-PD-1) are in clinical use for the treatment of cancer, yet their efficacy is limited. Pre-approved therapies that enhance the effect of anti-PD-1 in combination are beneficial. Small-molecule inhibitors that attenuate T cell receptor signaling are reported to prevent T cell exhaustion and induce memory T cells with stem cell potential, resulting in a durable effector T cell response in combination with anti-PD-1. In search of such targets, we focused on protein kinase D (PKD), which is suggested to be suppressive in both tumor growth and TCR signaling. We report that CRT0066101, a PKD inhibitor (PKDi), suppressed the growth of mouse tumors at a sub-micromolar concentration in vitro. Despite its inhibitory effects on tumors, a single treatment of tumor-bearing mice with PKDi did not inhibit, but rather accelerated tumor growth, and reversed the therapeutic effect of anti-PD-1. Mice treated with PKDi showed reduced T cell infiltration and defects in the generation of effector T cells, compared to those treated with anti-PD-1, suggesting that PKDi inhibited ongoing antitumor responses. Mechanistically, PKDi inhibited phosphorylation of AKT, a primary checkpoint that is reactivated by anti-PD-1. In conclusion, PKD is fundamentally required for T cell reactivation by anti-PD-1; therefore, inhibition of PKD is not appropriate for combination therapy with anti-PD-1. On the other hand, a single dose of PKDi was shown to strongly suppress experimental autoimmunity in mice, indicating that PKDi could be useful for the treatment of immune-related adverse events that are frequently reported in anti-PD-1 therapy.

Construction and Validation of a UPR-Associated Gene Prognostic Model for Head and Neck Squamous Cell Carcinoma

Our study is aimed at constructing and validating a UPR-associated gene signature to predict HNSCC prognosis. We obtained 544 samples of RNA sequencing data and clinical characteristics from TCGA database and randomly grouped the samples into training and testing cohorts (1 : 1 ratio). After identifying 14 UPR-associated genes with LASSO and univariate Cox regression analysis, HNSCC samples were categorized into low-risk (LR) and high-risk (HR) subgroups depending on the risk score. Our analyses indicated that low-risk patients had a much better prognosis in the training and testing cohorts. To predict the HNSCC prognosis with the 14 UPR-associated gene signatures, we incorporated the UPR gene risk score, N stage, M stage, and age into a nomogram model. We further explored the sensitivity to anticancer drugs by using the IC50 analysis in two subgroups from the Cancer Genome Project database. The outcomes showed that the AKT inhibitor III and sorafenib were sensitive anticancer drugs in HR and LR patients, respectively. The immune cell infiltration analysis and GSEA provided strong evidence for elucidating the molecular mechanisms of UPR-associated genes affecting HNSCC. In conclusion, the UPR-associated gene risk score, N stage, M stage, and age can serve as a robust model for predicting prognosis and can improve decision-making at the individual patient level.

Curdlan-Based Hydrogels for Potential Application as Dressings for Promotion of Skin Wound Healing-Preliminary In Vitro Studies

The aim of this work was to establish whether novel curdlan-based hydrogels enriched with Ca²⁺ ions may be considered as potential candidates for dressings, for the acceleration of skin wound healing. Firstly, biomaterials were allocated for evaluation of structural and mechanical properties. Subsequently, the ability of hydrogels to absorb simulated wound fluid and water vapor permeability, as well their capacity to release calcium ions, was evaluated. The biocompatibility of biomaterials was assessed using normal human skin fibroblasts. Importantly, the main features of the obtained curdlan-based hydrogels were compared with those of KALTOSTAT^® (a commercial calcium sodium alginate wound dressing). The obtained results showed that curdlan-based biomaterials possessed a mesoporous structure (pore diameter ranged from 14–48 nm) and exhibited a good ability to absorb simulated wound fluid (swelling ratio close to 974–1229%). Moreover, in a wet state, they enabled proper water vapor transmission rate (>2000 g/m²/day), thanks to their hydrogel structure. Finally, it was found that biomaterial composed of 11 wt.% of curdlan (Cur_11%) possessed the most desirable biological properties in vitro. It released a beneficial amount of calcium ions to the aqueous environment (approximately 6.12 mM), which significantly enhanced fibroblast viability and proliferation. Taking into account the beneficial properties of Cur_11% biomaterial, it seems justified to subject it to more advanced cell culture experiments in vitro and to in vivo studies in order to determine its precise influence on skin wound healing.

Evaluating the current status of protein kinase C (PKC)-protein kinase D (PKD) signalling axis as a novel therapeutic target in ovarian cancer

Ovarian cancer, especially high grade serous ovarian cancer is one of the most lethal gynaecological malignancies with high relapse rate and patient death. Notwithstanding development of several targeted treatment and immunotherapeutic approaches, researchers fail to turn ovarian cancer into a manageable disease. Protein kinase C (PKC) and protein kinase D (PKD) are families of evolutionarily conserved serine/threonine kinases that can be activated by a plethora of extracellular stimuli such as hormones, growth factors and G-protein coupled receptor agonists. Recent literature suggests that a signalling cascade initiated by these two protein kinases regulates a battery of cellular and physiological processes involved in tumorigenesis including cell proliferation, migration, invasion and angiogenesis. In an urgent need to discover novel therapeutic interventions against a deadly pathology like ovarian cancer, we have discussed the status quo of PKC/PKD signalling axis in context of this disease. Additionally, apart from discussing the structural properties and activation mechanisms of PKC/PKD, we have provided a comprehensive review of the recent reports on tumor promoting functions of PKC isoforms and discussed the potential of PKC/PKD signalling axis as a novel target in this lethal pathology. Furthermore, in this review, we have discussed the significance of several recent clinical trials and development of small molecule inhibitors that target PKC/PKD signalling axis in ovarian cancer.

Germline Mutation of PLCD1 Contributes to Human Multiple Pilomatricomas through Protein Kinase D/Extracellular Signal-Regulated Kinase1/2 Cascade and TRPV6

Pilomatricoma, a benign skin appendage tumor, also known as calcifying epithelioma, consists of islands of epithelial cells histologically that contain anucleated cells in the center surrounded by basophilic cells and partial calcification. Sporadic pilomatricomas commonly have somatic mutations in the gene CTNNB1, but causative genes from germline and the underlying pathophysiology are unclear. In this study, we identified a germline missense variant of PLCD1 encoding PLCδ1, c.1186G>A (p.Glu396Lys), in a large Chinese family with autosomal dominant multiple pilomatricomas. Phospholipase C, a key enzyme playing critical roles in intracellular signal transduction, is essential for epidermal barrier integrity. The p.Glu396Lys variant increased the enzymatic activity of PLCδ1, leading to protein kinase C/protein kinase D/extracellular signal-regulated kinase1/2 pathway activation and TPRV6 channel closure, which not only resulted in excessive proliferation of keratinocytes in vitro and in vivo but also induced local accumulation of calcium in the pilomatricoma-like tumor that developed spontaneously in the skin of Plcd1^E396K/E396K mice. Our results implicate this p.Glu396Lys variant of PLCD1 from germline leading to gain-of-function of PLCδ1 as a causative genetic defect in familial multiple pilomatricomas.

Human Testis Phosphoproteome Reveals Kinases as Potential Targets in Spermatogenesis and Testicular Cancer

Spermatogenesis is a complex cell differentiation process that includes marked genetic, cellular, functional and structural changes. It requires tight regulation, because disturbances in any of the spermatogenic processes would lead to fertility deficiencies as well as disorders in offspring. To increase our knowledge of signal transduction during sperm development, we carried out a large-scale identification of the phosphorylation events that occur in the human male gonad. Metal oxide affinity chromatography using TiO2 combined with LC-MS/MS was conducted to profile the phosphoproteome of adult human testes with full spermatogenesis. A total of 8187 phosphopeptides derived from 2661 proteins were identified, resulting in the most complete report of human testicular phosphoproteins to date. Phosphorylation events were enriched in proteins functionally related to spermatogenesis, as well as to highly active processes in the male gonad, such as transcriptional and translational regulation, cytoskeleton organization, DNA packaging, cell cycle and apoptosis. Moreover, 174 phosphorylated kinases were identified. The most active human protein kinases in the testis were predicted both by the number of phosphopeptide spectra identified and the phosphorylation status of the kinase activation loop. The potential function of cyclin-dependent kinase 12 (CDK12) and p21-activated kinase 4 (PAK4) has been explored by in silico, protein-protein interaction analysis, immunodetection in testicular tissue, and a functional assay in a human embryonal carcinoma cell line. The colocalization of CDK12 with Golgi markers suggests a potential crucial role of this protein kinase during sperm formation. PAK4 has been found expressed in human spermatogonia, and a role in embryonal carcinoma cell response to apoptosis has been observed. Together, our protein discovery analysis confirms that phosphoregulation by protein kinases is highly active in sperm differentiation and opens a window to detailed characterization and validation of potential targets for the development of drugs modulating male fertility and tumor behavior.

Oncogenic functions of protein kinase D2 and D3 in regulating multiple cancer-related pathways in breast cancer

Protein Kinase D (PKD) family contains PKD1, PKD2, and PKD3 in human. Compared to consistent tumor-suppressive functions of PKD1 in breast cancer, how PKD2/3 functions in breast cancer are not fully understood. In the current study, we found that PKD2 and PKD3 but not PKD1 were preferentially overexpressed in breast cancer and involved in regulating cell proliferation and metastasis. Integrated phosphoproteome, transcriptome, and interactome showed that PKD2 was associated with multiple cancer-related pathways, including adherent junction, regulation of actin cytoskeleton, and cell cycle-related pathways. ELAVL1 was identified as a common hub-node in networks of PKD2/3-regulated phosphoproteins and genes. Silencing ELAVL1 inhibited breast cancer growth in vitro and in vivo. Direct interaction between ELAVL1 and PKD2 or PKD3 was demonstrated. Suppression of PKD2 led to ELAVL1 translocation from the cytoplasm to the nucleus without significant affecting ELAVL1 expression. Taken together, we characterized the oncogenic functions of PKD2/3 in breast cancer and their association with cancer-related pathways, which shed lights on the oncogenic roles and mechanisms of PKDs in breast cancer.

Protein kinase D signaling in cancer: A friend or foe?

Protein kinase D is a family of evolutionarily conserved serine/threonine kinases that belongs to the Ca⁺⁺/Calmodulin-dependent kinase superfamily. Signal transduction pathways mediated by PKD can be triggered by a variety of stimuli including G protein-coupled receptor agonists, growth factors, hormones, and cellular stresses. The regulatory mechanisms and physiological roles of PKD have been well documented including cell proliferation, survival, migration, angiogenesis, regulation of gene expression, and protein/membrane trafficking. However, its precise roles in disease progression, especially in cancer, remain elusive. A plethora of studies documented the cell- and tissue-specific expressions and functions of PKD in various cancer-associated biological processes, while the causes of the differential effects of PKD have not been thoroughly investigated. In this review, we have discussed the structural-functional properties, activation mechanisms, signaling pathways and physiological functions of PKD in the context of human cancer. Additionally, we have provided a comprehensive review of the reported tumor promoting or tumor suppressive functions of PKD in several major cancer types and discussed the discrepancies that have been raised on PKD as a major regulator of malignant transformation.

Tailoring the delivery of therapeutic ions from bioactive scaffolds while inhibiting their apatite nucleation: a coaxial electrospinning strategy for soft tissue regeneration

Control the release of ions as a function of the shell thickness. Inhibit hydroxyapatite nucleation. Improve mechanical properties.

Activation of PI3K signaling prevents aminoglycoside-induced hair cell death in the murine cochlea

Loss of sensory hair cells of the inner ear due to aminoglycoside exposure is a major cause of hearing loss. Using an immortalized multipotent otic progenitor (iMOP) cell line, specific signaling pathways that promote otic cell survival were identified. Of the signaling pathways identified, the PI3K pathway emerged as a strong candidate for promoting hair cell survival. In aging animals, components for active PI3K signaling are present but decrease in hair cells. In this study, we determined whether activated PI3K signaling in hair cells promotes survival. To activate PI3K signaling in hair cells, we used a small molecule inhibitor of PTEN or genetically ablated PTEN using a conditional knockout animal. Hair cell survival was challenged by addition of gentamicin to cochlear cultures. Hair cells with activated PI3K signaling were more resistant to aminoglycoside-induced hair cell death. These results indicate that increased PI3K signaling in hair cells promote survival and the PI3K signaling pathway is a target for preventing aminoglycoside-induced hearing loss.

Fructose Containing Sugars at Normal Levels of Consumption Do Not Effect Adversely Components of the Metabolic Syndrome and Risk Factors for Cardiovascular Disease

The objective of the current study was to explore our hypothesis that average consumption of fructose and fructose containing sugars would not increase risk factors for cardiovascular disease (CVD) and the metabolic syndrome (MetS). A randomized, double blind, parallel group study was conducted where 267 individuals with BMI between 23 and 35 kg/m² consumed low fat sugar sweetened milk, daily for ten weeks as part of usual weight-maintenance diet. One group consumed 18% of calories from high fructose corn syrup (HFCS), another group consumed 18% of calories from sucrose, a third group consumed 9% of calories from fructose, and the fourth group consumed 9% of calories from glucose. There was a small change in waist circumference (80.9 ± 9.5 vs. 81.5 ± 9.5 cm) in the entire cohort, as well as in total cholesterol (4.6 ± 1.0 vs. 4.7 ± 1.0 mmol/L, p < 0.01), triglycerides (TGs) (11.5 ± 6.4 vs. 12.6 ± 8.9 mmol/L, p < 0.01), and systolic (109.2 ± 10.2 vs. 106.1 ± 10.4 mmHg, p < 0.01) and diastolic blood pressure (69.8 ± 8.7 vs. 68.1 ± 9.7 mmHg, p < 0.01). The effects of commonly consumed sugars on components of the MetS and CVD risk factors are minimal, mixed and not clinically significant.

Opposing growth regulatory roles of protein kinase D isoforms in human keratinocytes

PKD is a family of three serine/threonine kinases (PKD-1, -2, and -3) involved in the regulation of diverse biological processes including proliferation, migration, secretion, and cell survival. We have previously shown that despite expression of all three isoforms in mouse epidermis, PKD1 plays a unique and critical role in wound healing, phorbol ester-induced hyperplasia, and tumor development. In translating our findings to the human, we discovered that PKD1 is not expressed in human keratinocytes (KCs) and there is a divergence in the expression and function of other PKD isoforms. Contrary to mouse KCs, treatment of cultured human KCs with pharmacological inhibitors of PKDs resulted in growth arrest. We found that PKD2 and PKD3 are expressed differentially in proliferating and differentiating human KCs, with the former uniformly present in both compartments whereas the latter is predominantly expressed in the proliferating compartment. Knockdown of individual PKD isoforms in human KCs revealed contrasting growth regulatory roles for PKD2 and PKD3. Loss of PKD2 enhanced KC proliferative potential while loss of PKD3 resulted in a progressive proliferation defect, loss of clonogenicity and diminished tissue regenerative ability. This proliferation defect was correlated with up-regulation of CDK4/6 inhibitor p15(INK4B) and induction of a p53-independent G1 cell cycle arrest. Simultaneous silencing of PKD isoforms resulted in a more pronounced proliferation defect consistent with a predominant role for PKD3 in proliferating KCs. These data underline the importance and complexity of PKD signaling in human epidermis and suggest a central role for PKD3 signaling in maintaining human epidermal homeostasis.

Protein kinase D1 deficiency promotes differentiation in epidermal keratinocytes

BACKGROUND

Protein kinase D (PKD or PKD1) is a serine/threonine protein kinase that has been shown to play a role in a variety of cellular processes; however, the function of PKD1 in the skin has not been fully investigated. The balance between proliferation and differentiation processes in the predominant cells of the epidermis, the keratinocytes, is essential for normal skin function.

OBJECTIVE

To investigate the effect of PKD1 deficiency on proliferation and differentiation of epidermal keratinocytes.

METHODS

We utilized a floxed PKD1 mouse model such that infecting epidermal keratinocytes derived from these mice with an adenovirus expressing Cre-recombinase allowed us to determine the effect of PKD1 gene loss in vitro. Proliferation and differentiation were monitored using qRT-PCR, Western blot, transglutaminase activity assays, [3H]thymidine incorporation into DNA and cell cycle analysis.

RESULTS

A significant decrease in PKD1 mRNA and protein levels was achieved in adenoviral Cre-recombinase-infected cells. Deficiency of PKD1 resulted in significant increases in the mRNA and protein expression of various differentiation markers such as loricrin, involucrin, and keratin 10 either basally and/or upon stimulation of differentiation. PKD1-deficient keratinocytes also showed an increase in transglutaminase expression and activity, indicating an anti-differentiative role of PKD1. Furthermore, the PKD1-deficient keratinocytes exhibited decreased proliferation. However, PKD1 loss had no effect on stem cell marker expression.

CONCLUSIONS

Cre-recombinase-mediated knockdown represents an additional approach demonstrating that PKD1 is an anti-differentiative, pro-proliferative signal in mouse keratinocytes.

VGF (TLQP-62)-induced neurogenesis targets early phase neural progenitor cells in the adult hippocampus and requires glutamate and BDNF signaling

The neuropeptide VGF (non-acronymic), which has antidepressant-like effects, enhances adult hippocampal neurogenesis as well as synaptic activity and plasticity in the hippocampus, however the interaction between these processes and the mechanism underlying this regulation remain unclear. In this study, we demonstrate that VGF-derived peptide TLQP-62 specifically enhances the generation of early progenitor cells in nestin-GFP mice. Specifically, TLQP-62 significantly increases the number of Type 2a neural progenitor cells (NPCs) while reducing the number of more differentiated Type 3 cells. The effect of TLQP-62 on proliferation rather than differentiation was confirmed using NPCs in vitro; TLQP-62 but not scrambled peptide PEHN-62 increases proliferation in a cell line as well as in primary progenitors from adult hippocampus. Moreover, TLQP-62 but not scrambled peptide increases Cyclin D mRNA expression. The proliferation of NPCs induced by TLQP-62 requires synaptic activity, in particular through NMDA and metabotropic glutamate receptors. The activation of glutamate receptors by TLQP-62 activation induces phosphorylation of CaMKII through NMDA receptors and protein kinase D through metabotropic glutamate receptor 5 (mGluR5). Furthermore, pharmacological antagonists to CaMKII and PKD inhibit TLQP-62-induced proliferation of NPCs indicating that these signaling molecules downstream of glutamate receptors are essential for the actions of TLQP-62 on neurogenesis. We also show that TLQP-62 gradually activates Brain-Derived Neurotrophic Factor (BDNF)-receptor TrkB in vitro and that Trk signaling is required for TLQP-62-induced proliferation of NPCs. Understanding the precise molecular mechanism of how TLQP-62 influences neurogenesis may reveal mechanisms by which VGF-derived peptides act as antidepressant-like agents.

Protein kinase D1 has a key role in wound healing and skin carcinogenesis

Protein kinase D (PKD) is a family of stress-responsive serine/threonine kinases implicated in the regulation of diverse cellular functions including cell growth, differentiation, apoptosis, and cell motility. Although all three isoforms are expressed in keratinocytes, their role in skin biology and pathology is poorly understood. We recently identified a critical role for PKD1 during reversal of keratinocyte differentiation in culture, suggesting a potential pro-proliferative role in epidermal adaptive responses. Here, we generated mice with targeted deletion of PKD1 in epidermis to evaluate the significance of PKD1 in normal and hyperplastic conditions. These mice displayed a normal skin phenotype indicating that PKD1 is dispensable for skin development and homeostasis. Upon wounding however, PKD1-deficient mice exhibited delayed wound re-epithelialization correlated with a reduced proliferation and migration of keratinocytes at the wound edge. In addition, the hyperplastic and inflammatory responses to topical phorbol ester were significantly suppressed suggesting involvement of PKD1 in tumor promotion. Consistently, when subjected to two-stage chemical skin carcinogenesis protocol, PKD1-deficient mice were resistant to papilloma formation when compared to control littermates. These results revealed a critical pro-proliferative role for PKD1 in epidermal adaptive responses, suggesting a potential therapeutic target in skin wound and cancer treatment.

Novel mechanism of cytokine-induced disruption of epithelial barriers: Janus kinase and protein kinase D-dependent downregulation of junction protein expression

The ductal epithelium plays a key role in physiological secretion of pancreatic enzymes into the digestive system. Loss of barrier properties of the pancreatic duct may contribute to the development of pancreatitis and metastatic dissemination of pancreatic tumors. Proinflammatory cytokines are essential mediators of pancreatic inflammation and tumor progression; however, their effects on the integrity and barrier properties of the ductal epithelium have not been previously addressed. In the present study, we investigate mechanisms of cytokine-induced disassembly of tight junctions (TJs) and adherens junctions (AJs) in a model pancreatic epithelium. Exposure of HPAF-II human pancreatic epithelial cell monolayers to interferon (IFN)γ disrupted integrity and function of apical junctions as manifested by increased epithelial permeability and cytosolic translocation of AJ and TJ proteins. Tumor necrosis factor (TNF)α potentiated the effects of IFNγ on pancreatic epithelial junctions. The cytokine-induced increase in epithelial permeability and AJ/TJ disassembly was attenuated by pharmacological inhibition of Janus kinase (JAK) and protein kinase D (PKD). Loss of apical junctions in IFNγ/TNFα-treated HPAF-II cells was accompanied by JAK and PKD dependent decrease in expression of AJ (E-cadherin, p120 catenin) and TJ (occludin, ZO-1) proteins. Depletion of E-cadherin or p120 catenin recapitulated the effects of cytokines on HPAF-II cell permeability and junctions. Our data suggests that proinflammatory cytokines disrupt pancreatic epithelial barrier via expressional downregulation of key structural components of AJs and TJs. This mechanism is likely to be important for pancreatic inflammatory injury and tumorigenesis.

PKD2 and PKD3 promote prostate cancer cell invasion by modulating NF-κB- and HDAC1-mediated expression and activation of uPA

Although protein kinase D3 (PKD3) has been shown to contribute to prostate cancer cell growth and survival, the role of PKD in prostate cancer cell motility remains unclear. Here, we show that PKD2 and PKD3 promote nuclear factor kappa B (NF-κB) signaling and urokinase-type plasminogen activator (uPA) expression/activation, which are crucial for prostate cancer cell invasion. Silencing of endogenous PKD2 and/or PKD3 markedly decreased prostate cancer cell migration and invasion, reduced uPA and uPA receptor (uPAR) expression and increased plasminogen activator inhibitor-2 (PAI-2) expression. These results were further substantiated by the finding that PKD2 and PKD3 promoted the activity of uPA and matrix metalloproteinase 9 (MMP9). Furthermore, depletion of PKD2 and/or PKD3 decreased the level of binding of the p65 subunit of NF-κB to the promoter of the gene encoding uPA (PLAU), suppressing transcriptional activation of uPA. Endogenous PKD2 and PKD3 interacted with inhibitor of NF-κB (IκB) kinase β (IKKβ); PKD2 mainly regulated the phosphorylated IKK (pIKK)-phosphorylated IκB (pIκB)-IκB degradation cascade, p65 nuclear translocation, and phosphorylation of Ser276 on p65, whereas PKD3 was responsible for the phosphorylation of Ser536 on p65. Conversely, inhibition of uPA transactivation by PKD3 silencing was rescued by constitutive Ser536 p65 phosphorylation, and reduced tumor cell invasion resulting from PKD2 or PKD3 silencing was rescued by ectopic expression of p65. Interestingly, PKD3 interacted with histone deacetylase 1 (HDAC1), suppressing HDAC1 expression and decreasing its binding to the uPA promoter. Moreover, depletion of HDAC1 resulted in recovery of uPA transactivation in PKD3-knockdown cells. Taken together, these data suggest that PKD2 and PKD3 coordinate to promote prostate cancer cell invasion through p65 NF-κB- and HDAC1-mediated expression and activation of uPA.

An RCT on the effects of topical CGP on surgical wound appearance and residual scarring in bilateral total-knee arthroplasty patients

OBJECTIVE

To test the hypothesis that topically applied calcium glycerophosphate (CGP) would improve the appearance of the wound following bilateral knee replacement.

METHOD

Healthy patients, aged 45-75 years, scheduled for bilateral total-knee replacement surgery were recruited into the study. One knee was randomly assigned to the treatment group, while the contralateral knee was designated the control (standard care). Subjects were instructed to apply a preparation of 10% CGP in an aqueous lotion to the treated knee once daily for 42 days, starting at the third postoperative day. Functional sealing and cosmetic appearance of the incision were evaluated by two surgeons by direct examination of the patient and then by two experienced assessors from photographs. The investigators qualitatively scored the intensity and extent of erythema along the incision and over the entire knee, the appearance of visible oedema along the incision and over the knee, and the overall clinical impression of wound healing. All four assessors were blinded to the subjects' allocation and the latter two assessors to the initial investigators' assessments. Subjects were also followed up for an additional 46 weeks, giving a total study duration of 12 months.

RESULTS

Twenty patients completed the study. Statistical analysis showed that both the area and intensity of erythema along the incision were significantly reduced in the treated vs untreated knee over the entire study period. The analysis further showed that treatment significantly reduced oedema, both along the incision and across the entire knee. The differences were most marked at the seventh postoperative day and diminished with time. No adverse effects were observed for any patient, in either treated or untreated knees.

CONCLUSION

These data demonstrate that postoperative application of 10% CGP could improve the appearance of the wound following total knee arthroplasty.

Calcium-based nanoparticles accelerate skin wound healing

Introduction

Nanoparticles (NPs) are small entities that consist of a hydroxyapatite core, which can bind ions, proteins, and other organic molecules from the surrounding environment. These small conglomerations can influence environmental calcium levels and have the potential to modulate calcium homeostasis in vivo. Nanoparticles have been associated with various calcium-mediated disease processes, such as atherosclerosis and kidney stone formation. We hypothesized that nanoparticles could have an effect on other calcium-regulated processes, such as wound healing. In the present study, we synthesized pH-sensitive calcium-based nanoparticles and investigated their ability to enhance cutaneous wound repair.

Methods

Different populations of nanoparticles were synthesized on collagen-coated plates under various growth conditions. Bilateral dorsal cutaneous wounds were made on 8-week-old female Balb/c mice. Nanoparticles were then either administered intravenously or applied topically to the wound bed. The rate of wound closure was quantified. Intravenously injected nanoparticles were tracked using a FLAG detection system. The effect of nanoparticles on fibroblast contraction and proliferation was assessed.

Results

A population of pH-sensitive calcium-based nanoparticles was identified. When intravenously administered, these nanoparticles acutely increased the rate of wound healing. Intravenously administered nanoparticles were localized to the wound site, as evidenced by FLAG staining. Nanoparticles increased fibroblast calcium uptake in vitro and caused contracture of a fibroblast populated collagen lattice in a dose-dependent manner. Nanoparticles also increased the rate of fibroblast proliferation.

Conclusion

Intravenously administered, calcium-based nanoparticles can acutely decrease open wound size via contracture. We hypothesize that their contraction effect is mediated by the release of ionized calcium into the wound bed, which occurs when the pH-sensitive nanoparticles disintegrate in the acidic wound microenvironment. This is the first study to demonstrate that calcium-based nanoparticles can have a therapeutic benefit, which has important implications for the treatment of wounds.

Protein kinase D signaling: multiple biological functions in health and disease

Protein kinase D (PKD) is an evolutionarily conserved protein kinase family with structural, enzymological, and regulatory properties different from the PKC family members. Signaling through PKD is induced by a remarkable number of stimuli, including G-protein-coupled receptor agonists and polypeptide growth factors. PKD1, the most studied member of the family, is increasingly implicated in the regulation of a complex array of fundamental biological processes, including signal transduction, cell proliferation and differentiation, membrane trafficking, secretion, immune regulation, cardiac hypertrophy and contraction, angiogenesis, and cancer. PKD mediates such a diverse array of normal and abnormal biological functions via dynamic changes in its spatial and temporal localization, combined with its distinct substrate specificity. Studies on PKD thus far indicate a striking diversity of both its signal generation and distribution and its potential for complex regulatory interactions with multiple downstream pathways, often regulating the subcellular localization of its targets.

Emerging roles of protein kinase D1 in cancer

Protein kinase D1 (PKD1) is a serine-threonine kinase that regulates various functions within the cell, including cell proliferation, apoptosis, adhesion, and cell motility. In normal cells, this protein plays key roles in multiple signaling pathways by relaying information from the extracellular environment and/or upstream kinases and converting them into a regulated intracellular response. The aberrant expression of PKD1 is associated with enhanced cancer phenotypes, such as deregulated cell proliferation, survival, motility, and epithelial mesenchymal transition. In this review, we summarize the structural and functional aspects of PKD1 and highlight the pathobiological roles of this kinase in cancer.

Unique functions for protein kinase D1 and protein kinase D2 in mammalian cells

Mammalian PKD (protein kinase D) isoforms have been implicated in the regulation of diverse biological processes in response to diacylglycerol and PKC (protein kinase C) signalling. To compare the functions of PKD1 and PKD2 in vivo, we generated mice deficient in either PKD1 or PKD2 enzymatic activity, via homozygous expression of PKD1^S744A/S748A or PKD2^S707A/S711A ‘knockin’ alleles. We also examined PKD2-deficient mice generated using ‘gene-trap’ technology. We demonstrate that, unlike PKD1, PKD2 catalytic activity is dispensable for normal embryogenesis. We also show that PKD2 is the major PKD isoform expressed in lymphoid tissues, but that PKD2 catalytic activity is not essential for the development of mature peripheral T- and B-lymphocytes. PKD2 catalytic activity is, however, required for efficient antigen receptor-induced cytokine production in T-lymphocytes and for optimal T-cell-dependent antibody responses in vivo. Our results reveal a key in vivo role for PKD2 in regulating the function of mature peripheral lymphocytes during adaptive immune responses. They also confirm the functional importance of PKC-mediated serine phosphorylation of the PKD catalytic domain for PKD activation and downstream signalling and reveal that different PKD family members have unique and non-redundant roles in vivo.

Ultraviolet B irradiation and activation of protein kinase D in primary mouse epidermal keratinocytes

Our previous studies demonstrated that protein kinase D (PKD), a serine/threonine kinase implicated in various cell processes, is up-regulated in basal cell carcinoma (BCC), supporting a possible tumorigenic role for PKD in skin. Since the greatest risk factor for BCC is sun exposure, the ability of ultraviolet B (UVB) irradiation to activate PKD in primary mouse keratinocytes was investigated. Using western analysis with two autophosphorylation-specific antibodies, we show for the first time that UVB activated PKD in a time- and dose-dependent manner. UVB-induced PKD activation was verified using an in vitro kinase assay. Furthermore, activation was reduced by antioxidant pretreatment, suggesting a link with oxidative stress. UVB-induced PKD activation was mediated primarily by Src family tyrosine kinases rather than protein kinase C (PKC), and in fact, UVB did not alter PKC-mediated transphosphorylation. UVB induced apoptosis dose-dependently, and this death could be prevented by overexpression of wild-type PKD, but not mutant PKD or the empty adenovirus. Indeed, a mutant that cannot be phosphorylated by Src kinases exacerbated UVB-elicited apoptosis. Thus, our data indicate that UVB irradiation of keratinocytes induces Src-mediated activation of PKD, which protects cells from UVB-stimulated apoptosis, providing a possible explanation for the observed up-regulation of PKD in BCC.