Protein kinase D1 regulates subcellular localisation and metastatic function of metastasis-associated protein 1

Protein kinase D activity is a risk biomarker in prostate cancer that drives cell invasion by a Snail/ERK dependent mechanism

Protein kinase D (PKD) family members play controversial roles in prostate cancer (PC). Thus, PKD1 is nearly absent in advanced tumours, where PKD2 and PKD3 are upregulated. Additionally, consequences of activation of these kinases on PC progression remain largely unclear. Here, we first investigated PKD function on PC cell motility, analysing the underlying molecular mechanisms. We find a striking decrease of Snail levels after PKD inhibition followed by cell migration and invasion impairment, demonstrating an unprecedented role of PKD activity on the regulation of this key transcription factor in PC progression. Specifically, we show that PKD2 activity mediates the effects of MEK/ERK pathway on Snail expression, establishing a joint function of ERK/PKD2/Snail cascade in PC cell invasion regulation. These results led us to address the clinical relevance of the correlation between PKD2 and ERK activities with Snail abundance in samples from PC patients at different stages, analysing its impact on tumour prognosis and patients´ survival. Importantly, this is the first study defining a direct correlation between active PKD2 and Snail levels, further linked to ERK activity. We also evidence that PKD2 activity is associated with important poor prognostic factors. Thus, PC patients with the expression pattern: active PKD2high/active ERKhigh/Snailhigh exhibit increased invasiveness and metastasis, and decreased survival. Our findings provide new insights for understanding the molecular mechanisms involved in PC progression, pinpointing the combination of active PKD2 and Snail levels, with the additional measurement of active ERK, as a confident biomarker to predict clinical outcome of patients with advanced PC.

MUC13 drives cancer aggressiveness and metastasis through the YAP1-dependent pathway

Anchorage-independent survival after intravasation of cancer cells from the primary tumor site represents a critical step in metastasis. Here, we reveal new insights into how MUC13-mediated anoikis resistance, coupled with survival of colorectal tumor cells, leads to distant metastasis. We found that MUC13 targets a potent transcriptional coactivator, YAP1, and drives its nuclear translocation via forming a novel survival complex, which in turn augments the levels of pro-survival and metastasis-associated genes. High expression of MUC13 is correlated well with extensive macrometastasis of colon cancer cells with elevated nuclear YAP1 in physiologically relevant whole animal model systems. Interestingly, a positive correlation of MUC13 and YAP1 expression was observed in human colorectal cancer tissues. In brief, the results presented here broaden the significance of MCU13 in cancer metastasis via targeting YAP1 for the first time and provide new avenues for developing novel strategies for targeting cancer metastasis.

MTA1 localizes to the mitotic spindle apparatus and interacts with TPR in spindle assembly checkpoint regulation

We previously identified a cell cycle-dependent periodic subcellular distribution of cancer metastasis-associated antigen 1 (MTA1) and unraveled a novel role of MTA1 in inhibiting spindle damage-induced spindle assembly checkpoint (SAC) activation in cancer cells. However, the more detailed subcellular localization of MTA1 in mitotic cells and its copartner in SAC regulation in cancer cells are still poorly understood. Here, through immunofluorescent colocalization analysis of MTA1 and alpha-tubulin in mitotic cancer cells, we reveal that MTA1 is dynamically localized to the spindle apparatus throughout the entire mitotic process. We also demonstrated a reversible upregulation of MTA1 expression upon spindle damage-induced SAC activation, and time-lapse imaging assays indicated that MTA1 silencing delayed the mitotic metaphase-anaphase transition in cancer cells. Further investigation revealed that MTA1 interacts and colocalizes with Translocated Promoter Region (TPR) on spindle microtubules in mitotic cells, and this interaction is attenuated on SAC activation. TPR is well-implicated in SAC regulation via binding the MAD1-MAD2 complex, however, no interactions between MTA1 and MAD1 or MAD2 were detected in our coimmunoprecipitation (co-IP) assays, suggesting that the MTA1-TPR may represent a distinct SAC-associated complex separate from the previously reported TPR-MAD1/MAD2 complex. Our data provide new insights into the subcellular localization and molecular function of MTA1 in SAC regulation in cancer, and indicate that intervention of the MTA1-TPR interaction may be effective to modulate SAC and hence chromosomal instability (CIN) in tumorigenesis.

Protein Kinase D1 Correlates with Less Lymph Node Metastasis Risk, Enhanced 5-FU Sensitivity, and Better Prognosis in Colorectal Cancer

Protein kinase D1 (PKD1) controls tumor growth and invasion of gastrointestinal tract-related cancers, but its prognostic role in colorectal cancer (CRC) is not clear yet. Therefore, this research intended to assess the potential of PKD1 as a marker for CRC patients' management, also to evaluate its effect on 5-fluorouracil (5-FU) chemosensitivity in CRC cell lines. PKD1 protein and mRNA expressions were measured by immunohistochemistry and reverse transcription-quantitative polymerase chain reaction assays in 214 CRC patients, respectively. The PKD1 overexpression plasmids and negative control (NC) plasmids were transfected into the HCT-116 and LoVo cell lines followed by 0-16 μM 5-FU treatment. PKD1 protein (P < 0.001) and mRNA expressions (P < 0.001) were both descended in tumor tissues compared to tumor-adjacent tissues. Meanwhile, tumor PKD1 protein and mRNA expressions were both negatively related to lymph node metastasis, N stage, and tumor-node-metastasis (TNM) stage (all P < 0.05). Prognostically, high expressions of PKD1 protein and mRNA were linked with prolonged disease-free survival (DFS) and overall survival (OS) (all P < 0.05). After adjustment by multivariate Cox analyses, PKD1 mRNA high expression independently forecasted longer DFS [hazard ratio (HR) = 0.199, P = 0.002] and OS (HR = 0.212, P = 0.022). In vitro experiments revealed that PKD1 overexpression decreased the half maximal inhibitory concentration value of 5-FU in the HCT-116 (P = 0.016) and LoVo (P = 0.007) cell lines. PKD1 expression links with less lymph node metastasis risk and satisfied prognosis in CRC patients, which promotes CRC cell chemosensitivity to 5-FU chemosensitivity as well.

Potential role for protein kinase D inhibitors in prostate cancer

Protein kinase D (PrKD), a novel serine-threonine kinase, belongs to a family of calcium calmodulin kinases that consists of three isoforms: PrKD1, PrKD2, and PrKD3. The PrKD isoforms play a major role in pathologic processes such as cardiac hypertrophy and cancer progression. The charter member of the family, PrKD1, is the most extensively studied isoform. PrKD play a dual role as both a proto-oncogene and a tumor suppressor depending on the cellular context. The duplicity of PrKD can be highlighted in advanced prostate cancer (PCa) where expression of PrKD1 is suppressed whereas the expressions of PrKD2 and PrKD3 are upregulated to aid in cancer progression. As understanding of the PrKD signaling pathways has been better elucidated, interest has been garnered in the development of PrKD inhibitors. The broad-spectrum kinase inhibitor staurosporine acts as a potent PrKD inhibitor and is the most well-known; however, several other novel and more specific PrKD inhibitors have been developed over the last two decades. While there is tremendous potential for PrKD inhibitors to be used in a clinical setting, none has progressed beyond preclinical trials due to a variety of challenges. In this review, we focus on PrKD signaling in PCa and the potential role of PrKD inhibitors therein, and explore the possible clinical outcomes based on known function and expression of PrKD isoforms at different stages of PCa.

Osteoblastic protein kinase D1 contributes to the prostate cancer cells dormancy via GAS6-circadian clock signaling

Disseminated prostate cancer (PCa) is known to have a strong propensity for bone marrow. These disseminated tumor cells (DTCs) can survive in bone marrow for years without obvious proliferation, while maintaining the ability to develop into metastatic lesions. However, how DTCs kept dormant and recur is still uncertain. Here, we focus on the role of osteoblastic protein kinase D1 (PKD1) in PCa (PC-3 and DU145) dormancy using co-culture experiments. Using flow cytometry, western blotting, and immunofluorescence, we observed that in co-cultures osteoblasts could induce a dormant state in PCa cells, which is manifested by a fewer cell divisions, a decrease Ki-67-positive populations and a lower ERK/p38 ratio. In contrast, silencing of PKD1 gene in osteoblasts impedes co-cultured prostate cancer cell's dormancy ability. Mechanismly, protein kinase D1 (PKD1) in osteoblasts induces PCa dormancy via activating CREB1, which promoting the expression and secretion of growth arrest specific 6 (GAS6). Furthermore, GAS6-induced dormancy signaling significantly increased the expression of core circadian clock molecules in PCa cells, and a negative correlation of circadian clock proteins (BMAL1, CLOCK and DEC2) with recurrence-free survival is observed in metastatic prostate cancer patients. Interestingly, the expression of cell cycle factors (p21, p27, CDK1 and PCNA) which regulated by circadian clock also upregulated in response to GAS6 stimulation. Taken together, we provide evidence that osteoblastic PKD1/CREB1/GAS6 signaling regulates cellular dormancy of PCa cells, and highlights the importance of circadian clock in PCa cells dormancy.

MTA1: A Vital Modulator in Prostate Cancer

Prostate cancer (PCa) is the most frequent cancer of the male genitourinary system and the second most common cancer in men worldwide. PCa has become one of the leading diseases endangering men's health in Asia in recent years, with a large increase in morbidity and mortality. MTA1 (metastasis-associated antigen-1), a transcriptional coregulator involved in histone deacetylation and nucleosome remodeling, is a member of the MTA family. MTA1 is involved in cell signaling, chromosomal remodeling, and transcriptional activities, all of which are important for epithelial cell progression, invasion, and growth. MTA1 has been demonstrated to play a significant role in the formation, progression, and metastasis of PCa, and MTA1 expression is specifically linked to PCa bone metastases. Therefore, MTA1 may be a potential target for PCa prevention and treatment. Here, we reviewed the structure, function, and expression of MTA1 in PCa as well as drugs that target MTA1 to highlight a potential new treatment for PCa.

Multifaceted Functions of Protein Kinase D in Pathological Processes and Human Diseases

Protein kinase D (PKD) is a family of serine/threonine protein kinases operating in the signaling network of the second messenger diacylglycerol. The three family members, PKD1, PKD2, and PKD3, are activated by a variety of extracellular stimuli and transduce cell signals affecting many aspects of basic cell functions including secretion, migration, proliferation, survival, angiogenesis, and immune response. Dysregulation of PKD in expression and activity has been detected in many human diseases. Further loss- or gain-of-function studies at cellular levels and in animal models provide strong support for crucial roles of PKD in many pathological conditions, including cancer, metabolic disorders, cardiac diseases, central nervous system disorders, inflammatory diseases, and immune dysregulation. Complexity in enzymatic regulation and function is evident as PKD isoforms may act differently in different biological systems and disease models, and understanding the molecular mechanisms underlying these differences and their biological significance in vivo is essential for the development of safer and more effective PKD-targeted therapies. In this review, to provide a global understanding of PKD function, we present an overview of the PKD family in several major human diseases with more focus on cancer-associated biological processes.

Cancer metastasis-associated protein 1 localizes to the nucleolus and regulates pre-rRNA synthesis in cancer cells

Metastasis-associated protein 1 (MTA1) is a critical component of the nucleosome remodeling and histone deacetylase (NuRD) complex. MTA1 has several biological functions, and it is closely associated with the malignant properties of human cancers; however, the mechanisms and subcellular localization of MTA1 in cells remain unclear. Some initial studies indicated that MTA1 was absent from the nucleolus; however, several NuRD components were recently found to be present in the nucleolus, where they regulate preribosomal RNA (pre-rRNA) transcription. In this study, we demonstrated that MTA1 is definitely localized to the nucleolus and regulates pre-rRNA transcription, which is consistent with the recent reports on NuRD. To determine if MTA1 was present in the nucleolus, we utilized the following complementary molecular approaches: immunofluorescence, GFP-tag tracking, immunoelectron microscopy, and immunoprecipitation (IP). To examine the role of MTA1 in rRNA synthesis, we performed quantitative polymerase chain reaction analysis. We revealed that both endogenous and exogenous MTA1 showed apparent granule-like nucleolar subcellular localization. MTA1 interacts with two major resident nucleolar proteins, nucleolin and nucleophosmin. Immunofluorescent colocalization analyses showed that MTA1 localizes to the fibrillarin-deficient regions of the nucleolus, and Co-IP experiments indicated that there was no interaction between MTA1 and fibrillarin; further, fibrillarin was not identified in the MTA1 interactome. Loss- and gain-of-function studies indicated that MTA1 promotes pre-rRNA transcription in cancer cells. Collectively, our data identify MTA1 as a novel nucleolar protein, and activation of pre-rRNA transcription in cancer cells may be an alternative mechanism by which MTA1 promotes malignancies.

Telangiectasia-ectodermal dysplasia-brachydactyly-cardiac anomaly syndrome is caused by de novo mutations in protein kinase D1

BACKGROUND

We describe two unrelated patients who display similar clinical features including telangiectasia, ectodermal dysplasia, brachydactyly and congenital heart disease.

METHODS

We performed trio whole exome sequencing and functional analysis using in vitro kinase assays with recombinant proteins.

RESULTS

We identified two different de novo mutations in protein kinase D1 (PRKD1, NM_002742.2): c.1774G>C, p.(Gly592Arg) and c.1808G>A, p.(Arg603His), one in each patient. PRKD1 (PKD1, HGNC:9407) encodes a kinase that is a member of the protein kinase D (PKD) family of serine/threonine protein kinases involved in diverse cellular processes such as cell differentiation and proliferation and cell migration as well as vesicle transport and angiogenesis. Functional analysis using in vitro kinase assays with recombinant proteins showed that the mutation c.1808G>A, p.(Arg603His) represents a gain-of-function mutation encoding an enzyme with a constitutive, lipid-independent catalytic activity. The mutation c.1774G>C, p.(Gly592Arg) in contrast shows a defect in substrate phosphorylation representing a loss-of-function mutation.

CONCLUSION

The present cases represent a syndrome, which associates symptoms from several different organ systems: skin, teeth, bones and heart, caused by heterozygous de novo mutations in PRKD1 and expands the clinical spectrum of PRKD1 mutations, which have hitherto been linked to syndromic congenital heart disease and limb abnormalities.

The phosphorylation status of PIP5K1C at serine 448 can be predictive for invasive ductal carcinoma of the breast

Phosphatidylinositol-4-phosphate 5-kinase type-1C (PIP5K1C) is a lipid kinase that regulates focal adhesion dynamics and cell attachment through site-specific formation of phosphatidylinositol-4,5-bisphosphate (PI4,5P₂). By comparing normal breast tissue to carcinoma in situ and invasive ductal carcinoma subtypes, we here show that the phosphorylation status of PIP5K1C at serine residue 448 (S448) can be predictive for breast cancer progression to an aggressive phenotype, while PIP5K1C expression levels are not indicative for this event. PIP5K1C phosphorylation at S448 is downregulated in invasive ductal carcinoma, and similarly, the expression levels of PKD1, the kinase that phosphorylates PIP5K1C at this site, are decreased. Overall, since PKD1 is a negative regulator of cell migration and invasion in breast cancer, the phosphorylation status of this residue may serve as an indicator of aggressiveness of breast tumors.