Protein kinase Calpha plays a critical role in mannosylerythritol lipid-induced differentiation of melanoma B16 cells

Promising Application, Efficient Production, and Genetic Basis of Mannosylerythritol Lipids

Mannosylerythritol lipids (MELs) are a class of glycolipids that have been receiving increasing attention in recent years due to their diverse biological activities. MELs are produced by certain fungi and display a range of bioactivities, making them attractive candidates for various applications in medicine, agriculture, and biotechnology. Despite their remarkable qualities, industrial-scale production of MELs remains a challenge for fungal strains. Excellent fungal strains and fermentation processes are essential for the efficient production of MELs, so efforts have been made to improve the fermentation yield by screening high-yielding strains, optimizing fermentation conditions, and improving product purification processes. The availability of the genome sequence is pivotal for elucidating the genetic basis of fungal MEL biosynthesis. This review aims to shed light on the applications of MELs and provide insights into the genetic basis for efficient MEL production. Additionally, this review offers new perspectives on optimizing MEL production, contributing to the advancement of sustainable biosurfactant technologies.

Apoptosis Induction in Murine Melanoma (B16F10) Cells by Mannosylerythritol Lipids-B; a Glycolipid Biosurfactant with Antitumoral Activities

Mannosylerythritol lipids have drawn attention to cosmetic and pharmaceutical industries due to their non-toxicity and excellent biological interactions with human skin, particularly with the deepest epidermal layer. Lamellar liquid crystal structure, formed by MEL-B, is an interesting feature due to its similarity to the stratum corneum molecular arrangement and cell signaling events involved in the deregulation of the cancerous cell membrane. Thus, this work aimed to evaluate the cytotoxicity of commercial mannosylerythritol lipids-B in murine melanoma, fibroblast, and human erythrocytes cells. Cytotoxic effect was more pronounced on the tumor cells from 20 µg/mL, reducing cell viability by 65%, whereas fibroblast and human erythrocytes cells were more resistant to glycolipid treatment. Fluorescence microscopy and flow cytometer proved that mannosylerythritol lipids-B is an apoptosis inducer in tumor cells related to reactive oxygen species generation.

The complexities of PKCα signaling in cancer

Protein kinase C α (PKCα) is a ubiquitously expressed member of the PKC family of serine/threonine kinases with diverse functions in normal and neoplastic cells. Early studies identified anti-proliferative and differentiation-inducing functions for PKCα in some normal tissues (e.g., regenerating epithelia) and pro-proliferative effects in others (e.g., cells of the hematopoietic system, smooth muscle cells). Additional well documented roles of PKCα signaling in normal cells include regulation of the cytoskeleton, cell adhesion, and cell migration, and PKCα can function as a survival factor in many contexts. While a majority of tumors lose expression of PKCα, others display aberrant overexpression of the enzyme. Cancer-related mutations in PKCα are uncommon, but rare examples of driver mutations have been detected in certain cancer types (e. g., choroid gliomas). Here we review the role of PKCα in various cancers, describe mechanisms by which PKCα affects cancer-related cell functions, and discuss how the diverse functions of PKCα contribute to tumor suppressive and tumor promoting activities of the enzyme. We end the discussion by addressing mutations and expression of PKCα in tumors and the clinical relevance of these findings.

Protein kinase C inhibitor anchored BRD4 PROTAC PEGylated nanoliposomes for the treatment of vemurafenib-resistant melanoma

Limited treatment options and development of resistance to targeted therapy within few months pose significant challenges in the treatment of BRAF-mutated malignant melanoma. Moreover, extensive angiogenesis and vasculogenic mimicry promote the rapid progression of disease. The purpose of this study was to develop a protein kinase C inhibitor anchored BRD4 PROTAC (ARV) loaded PEGylated nanoliposomes (LARPC). Palmitoyl-dl-carnitine chloride (PC) was used as a protein kinase C inhibitor to provide a cationic surface charge to LARPC. The formulation was characterized for particle size, zeta potential, drug release and various cell culture assays using HUVEC and vemurafenib resistant melanoma cells. The particle size of LARPC was found to be 105.25 ± 2.76 nm with a zeta potential of +26.6 ± 6.25 mV. Inhibition of angiogenesis was demonstrated by ARV and LARPC using human umbilical vein endothelial cells (HUVEC)-based matrigel basement membrane model. Additionally, LARPC demonstrated very low IC50 with promising inhibition of vasculogenic mimicry channel formation, cell migration as well as colony formation in vemurafenib-resistant melanoma cell lines. Hence, the outcome of this combination therapy indicated the suitability of LARPC as a potential and novel approach for eradicating vemurafenib-resistant melanoma.

Biological activity of mannosylerythritol lipids on the mammalian cells

Mannosylerythritol lipids (MEL) are glycolipids mainly produced by pseudo-yeasts. These molecules present remarkable biological activities widely explored in many fields, including medicine, pharmaceuticals, and cosmetics. This review presents the main biological activity of MEL on the HL60, K562, B16, PC12, and skin cells. There is strong evidence that MEL changes the levels of glycosphingolipids of HL-60 lineage, which induce differentiation into granulocytic cells. Regarding B16 cells, MEL can trigger both apoptosis (10 μM) and cell differentiation (5 μM), in which the MEL concentration is related to each metabolic pathway. MEL can also trigger differentiation in PC12 cells due to the increase in the GalCer content. In this specific case, the effects are transient, and the differentiated cells are unstable and tend to apoptosis. MEL-B can particularly maintain skin hydration and moisture due to their self-assembled structures that resemble the tissue cells. Moreover, MEL-B repair aquaporin expression in the HaCaT keratinocytes damaged with UVA irradiation, whereas MEL-C suppresses the expression of COX-2 protein in fibroblasts, indicating that these glycolipids activate the cellular antioxidant mechanism. Recent findings denoted the anti-melanogenic activity of MEL since they suppress tyrosinase enzyme at mRNA levels in B16 and NHMs cells. MEL act effectively on mammalian cells; however, there is no clear pattern of their metabolic effects. Also, gene expression levels seem to be related to two main factors: chemical structure and concentration. However, the specific signaling cascades that are induced by MEL remain inconclusive. Thus, further investigations are vital to understanding these mechanisms clearly. KEY POINTS: • The four MEL homologs promote different biological responses in mammalian cells. • MEL modifies the pattern of glycosphingolipids in the plasma membrane of tumor cells. • Activation/deactivation of phosphorylation of serine/threonine kinase proteins.

Surface Active Agents and Their Health-Promoting Properties: Molecules of Multifunctional Significance

Surface active agents (SAAs) are molecules with the capacity to adsorb to solid surfaces and/or fluid interfaces, a property that allows them to act as multifunctional ingredients (e.g., wetting and dispersion agents, emulsifiers, foaming and anti-foaming agents, lubricants, etc.) in a widerange of the consumer products of various industrial sectors (e.g., pharmaceuticals, cosmetics, personal care, detergents, food, etc.). Given their widespread utilization, there is a continuously growing interest to explore their role in consumer products (relevant to promoting human health) and how such information can be utilized in order to synthesize better chemical derivatives. In this review article, weaimed to provide updated information on synthetic and biological (biosurfactants) SAAs and their health-promoting properties (e.g., anti-microbial, anti-oxidant, anti-viral, anti-inflammatory, anti-cancer and anti-aging) in an attempt to better define some of the underlying mechanism(s) by which they exert such properties.

Mannosylerythritol lipids: antimicrobial and biomedical properties

Mannosylerythritol lipids (MELs) have attracted particular interest of medical, pharmaceutical, and cosmetic fields, due to their specific characteristics, including non-toxicity, easy biodegradability, and environmental compatibility. Therefore, this review aims to highlight recent findings on MEL biological properties, focusing on issues related to therapeutic applications. Among the main findings is that MELs can play a fundamental role due to their antimicrobial properties against several nosocomial pathogen microorganisms. Other remarkable biological properties of MELs are related to skincare, as antiaging (active agent), and in particular on recover of skin cells that were damaged by UV radiation. MEL is also related to the increased efficiency of DNA transfection in liposome systems. Regarding the health field, these glycolipids seem to be associated with disturbance in the membrane composition of cancerous cells, increasing expression of genes responsible for cytoplasmic stress and apoptosis. Moreover, MELs can be associated with nanoparticles, as a capping agent, also acting to increase the solubility and cytotoxicity of them. Furthermore, the differences in the chemical structure of MEL could improve and expand their biochemical diversity and applications. Such modifications could change their interfacial properties and, thus, reduce the surface tension value, enhance the solubility, lower critical micelle concentrations, and form unique self-assembly structures. The latest is closely related to molecular recognition and protein stabilization properties of MEL, that is, essential parameters for their effective cosmetical and pharmaceutical effects. Thus, this current research indicates the huge potential of MEL for use in biomedical formulations, either alone or in combination with other molecules.

Production and characterization of a new glycolipid, mannosylerythritol lipid, from waste cooking oil biotransformation by Pseudozyma aphidis ZJUDM34

Mannosylerythritol lipids (MELs) are glycolipids possessing unique biosurfactant properties. However, the prices of substrates currently used for MEL formation caused its unsustainable commercial development. Waste cooking oil poses significant ecological and economical problems. Thus, the production of MELs from used waste cooking oil using the biotransformation route is one of the better alternatives to utilize it efficiently and economically. This work aims at the production of MELs using waste cooking oil instead of soybean oil and evaluating the major characteristics and compositions of MELs. The titers reached 61.50 g/L by the optimization of culture medium, higher than the counterpart (10.25 ± 0.32 g/L) of the nonoptimized medium. MELs exhibited good surface activity and better performance in contrast to MELs grown on soybean oil. The water phase behavior of MEL-A was also evaluated. The process showed higher productivity of MELs with better surface activity and application stability than the conventional process using soybean oil. The findings of this study imply that the use of inexpensive fermentation substrates associated with straightforward downstream processing is expected to have a great impact on the economy of MEL production.

Tailor-made mannosylerythritol lipids: current state and perspectives

Mannosylerythritol lipids (MELs) are a type of glycolipid biosurfactant produced by basidiomycetous yeasts, most notably those belonging to the genera Pseudozyma and Ustilago. Mannosylerythritol lipids are environmentally friendly and possess many unique functions, such as gene delivery, bio-activation, and human skin repair, and thus have potential applications in cosmetic, pharmaceutical, agriculture, food, and environmental industries. However, MELs will require overcoming same issues related to the commercialization, e.g., expansion of the structure and function variety and cost reduction. In the past decade, various studies have attempted to tailor production of targeted MELs in order to expand the utility of these biosurfactants. Moreover, the rapid development of genomic sequencing techniques will enhance our ability to modify MEL producers. In this review, we focus on current research into the tailored production of MELs, including conventional and advanced approaches.

Protein kinase C-α and the regulation of diverse cell responses

Protein kinase C (PKC) comprises a family of lipid-sensitive enzymes that have been involved in a broad range of cellular functions. PKC-α is a member of classical PKC with ubiquitous expression and different cellular localization. This unique PKC isoform is activated by various signals which evoke lipid hydrolysis, after activation it interacts with various adapter proteins and is localized to specific cellular compartments where it is devised to work. The universal expression and activation by various stimuli make it a perfect player in uncountable cellular functions including differentiation, proliferation, apoptosis, cellular transformation, motility, adhesion and so on. However, these functions are not intrinsic properties of PKC-α, but depend on cell types and conditions. The activities of PKC-α are managed by the various pharmacological activators/inhibitors and antisense oligonucleotides. The aim of this review is to elaborate the structural feature, and provide an insight into the mechanism of PKC-α activation and regulation of its key biological functions in different cellular compartments to develop an effective pharmacological approach to regulate the PKC-α signal array.

Amphiphilic glycoconjugates as potential anti-cancer chemotherapeutics

Amphiphilicity is one of the desirable features in the process of drug development which improves the biological as well as the pharmacokinetics profile of bioactive molecule. Carbohydrate moieties present in anti-cancer natural products and synthetic molecules influence the amphiphilicity and hence their bioactivity. This review focuses on natural and synthetic amphiphilic anti-cancer glycoconjugates. Different classes of molecules with varying degree of amphiphilicity are covered with discussions on their structure-activity relationship and mechanism of action.

Current status in biotechnological production and applications of glycolipid biosurfactants

Biosurfactants are natural compounds with surface activity and emulsifying properties produced by several types of microorganisms and have been considered an interesting alternative to synthetic surfactants. Glycolipids are promising biosurfactants, due to low toxicity, biodegradability, and chemical stability in different conditions and also because they have many biological activities, allowing wide applications in different fields. In this review, we addressed general information about families of glycolipids, rhamnolipids, sophorolipids, mannosylerythritol lipids, and trehalose lipids, describing their chemical and surface characteristics, recent studies using alternative substrates, and new strategies to improve of production, beyond their specificities. We focus in providing recent developments and trends in biotechnological process and medical and industrial applications.

Differentiation-inducing and anti-proliferative activities of isoliquiritigenin and all-trans-retinoic acid on B16F0 melanoma cells: Mechanisms profiling by RNA-seq

Melanoma is a cancer that arises from melanocytes, specialized pigmented cells that are found predominantly in the skin. The incidence of malignant melanoma has significantly increased over the last decade. With the development of therapy, the survival rate of some kind of cancer has been improved greatly. But the treatment of melanoma remains unsatisfactory. Much of melanoma's resistance to traditional chemotherapy is believed to arise intrinsically, by virtue of potent growth and cell survival-promoting genetic alteration. Therefore, significant attention has recently been focused on differentiation therapy, as well as differentiation inducer compounds. In previous study, we found isoliquiritigenin (ISL), a natural product extracted from licorice, could induce B16F0 melanoma cell differentiation. Here we investigated the transcriptional response of melanoma differentiation process induced by ISL and all-trans-retinoic acid (RA). Results showed that 390 genes involves in 201 biochemical pathways were differentially expressed in ISL treatment and 304 genes in 193 pathways in RA treatment. Differential expressed genes (DGEs, fold-change (FC)≥10) with the function of anti-proliferative and differentiation inducing indicated a loss of grade malignancy characteristic. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis indicated glutathione metabolism, glycolysis/gluconeogenesis and pentose phosphate pathway were the top three relative pathway perturbed by ISL, and mitogen-activated protein kinase (MAPK) signaling pathway was the most important pathway in RA treatment. In the analysis of hierarchical clustering of DEGs, we discovered 72 DEGs involved in the process of drug action. We thought Cited1, Tgm2, Xaf1, Cd59a, Fbxo2, Adh7 may have critical role in the differentiation of melanoma. The evidence displayed herein confirms the critical role of reactive oxygen species (ROS) in melanoma pathobiology and provides evidence for future targets in the development of next-generation biomarkers and therapeutics.

Characterization and Inducing Melanoma Cell Apoptosis Activity of Mannosylerythritol Lipids-A Produced from Pseudozyma aphidis

Mannosylerythritol lipids (MELs) are natural glycolipid biosurfactants which have potential applications in the fields of food, cosmetic and medicine. In this study, MELs were produced from vegetable oil by Pseudozyma aphidis. Their structural data through LC/MS, GC/MS and NMR analysis revealed that MEL-A with two acetyls was the major compound and the identified homologs of MEL-A contained a length of C8 to C14 fatty acid chains. This glycolipid exhibited a surface tension of 27.69 mN/m at a critical micelle concentration (CMC), self-assembling into particles in the water solution. It was observed to induce cell growth-inhibition and apoptosis of B16 melanoma cells in a dose-dependent manner, as well as cause cell cycle arrest at the S phase. Further quantitative RT-PCR analysis and western blotting revealed an increasing tendency of both mRNA and protein expressions of Caspase-12, CHOP, GRP78 and Caspase-3, and a down-regulation of protein Bcl-2. Combined with the up regulation of signaling IRE1 and ATF6, it can be speculated that MEL-A-induced B16 melanoma cell apoptosis was associated with the endoplasmic reticulum stress (ERS).

Mannosylerythritol lipids: production and applications

Mannosylerythritol lipids (MELs) are a glycolipid class of biosurfactants produced by a variety yeast and fungal strains that exhibit excellent interfacial and biochemical properties. MEL-producing fungi were identified using an efficient screening method for the glycolipid production and taxonomical classification on the basis of ribosomal RNA sequences. MEL production is limited primarily to the genus Pseudozyma, with significant variability among the MEL structures produced by each species. Outside of Pseudozyma, one recently isolated strain, Ustilago scitaminea, has been shown to exhibit abundant MEL-B production from sugarcane juice. Structural analyses of these compounds suggest a role for MELs in numerous cosmetic applications. MELs act as effective topical moisturizers and can repair damaged hair. Furthermore, these compounds have been shown to exhibit both protective and healing activities, to activate fibroblasts and papilla cells, and to act as natural antioxidants. In this review, we provide a brief summary of MEL research over the past few decades, focusing on the identification of MEL-producing fungi, the structural characterization of MELs, the use of alternative compounds as a primary carbon source, and the use of these compounds in cosmetic applications.

Characteristics of mannosylerythritol lipids and their environmental potential

Mannosylerythritol lipids (MELs) are promising biosurfactants containing two glycosyl derivatives and various fatty acids, which are mainly secreted by Pseudozyma as well as Ustilago. In this review, the latest research is demonstrated on production conditions, structural diversity, self-assembling properties and versatile biochemical functions of MELs. The genetic study and synthetic pathways, which mainly influence the type and yield of MELs production. Due to the excellent surface activity, biocompatibility and restorative function, MELs can be used in enviornmental industry, which has not been widely noted. In this paper, the current status of research on enviornmental potential of MELs has been discussed including petroleum degradation, bioconversion of chemical wastes and enhanced bioremediation of amphiphilic wastes.

Conversion of cellulosic materials into glycolipid biosurfactants, mannosylerythritol lipids, by Pseudozyma spp. under SHF and SSF processes

Background

Mannosylerythritol lipids (MEL) are glycolipids with unique biosurfactant properties and are produced by Pseudozyma spp. from different substrates, preferably vegetable oils, but also sugars, glycerol or hydrocarbons. However, solvent intensive downstream processing and the relatively high prices of raw materials currently used for MEL production are drawbacks in its sustainable commercial deployment. The present work aims to demonstrate MEL production from cellulosic materials and investigate the requirements and consequences of combining commercial cellulolytic enzymes and Pseudozyma spp. under separate hydrolysis and fermentation (SHF) and simultaneous saccharification and fermentation (SSF) processes.

Results

MEL was produced from cellulosic substrates, Avicel® as reference (>99% cellulose) and hydrothermally pretreated wheat straw, using commercial cellulolytic enzymes (Celluclast 1.5 L® and Novozyme 188®) and Pseudozyma antarctica PYCC 5048^T or Pseudozyma aphidis PYCC 5535^T. The strategies included SHF, SSF and fed-batch SSF with pre-hydrolysis. While SSF was isothermal at 28°C, in SHF and fed-batch SSF, yeast fermentation was preceded by an enzymatic (pre-)hydrolysis step at 50°C for 48 h. Pseudozyma antarctica showed the highest MEL yields from both cellulosic substrates, reaching titres of 4.0 and 1.4 g/l by SHF of Avicel® and wheat straw (40 g/l glucan), respectively, using enzymes at low dosage (3.6 and 8.5 FPU/g_glucan at 28°C and 50°C, respectively) with prior dialysis. Higher MEL titres were obtained by fed-batch SSF with pre-hydrolysis, reaching 4.5 and 2.5 g/l from Avicel® and wheat straw (80 g/l glucan), respectively.

Conclusions

This work reports for the first time MEL production from cellulosic materials. The process was successfully performed through SHF, SSF or Fed-batch SSF, requiring, for maximal performance, dialysed commercial cellulolytic enzymes. The use of inexpensive lignocellulosic substrates associated to straightforward downstream processing from sugary broths is expected to have a great impact in the economy of MEL production for the biosurfactant market, inasmuch as low enzyme dosage is sufficient for good systems performance.

Microbial amphiphiles: a class of promising new-generation anticancer agents

Developing new classes of anticancer molecules has always been a major scientific challenge owing to multidrug resistance of cancer cells to conventional chemotherapeutic agents. Microbial amphiphiles, particularly lipopeptides and glycolipids, have recently emerged as potential new-generation anticancer agents, owing to low toxicity, high efficacy and easy biodegradability. They exhibit anticancer activities by retarding cell cycle progression, inhibiting crucial signaling pathways such as Akt, extracellular signal-regulated kinase/c-Jun N-terminal kinase (ERK/JNK) and Janus kinase/signal transducer and activator of transcription (JAK/STAT), reducing angiogenesis, activating natural killer T (NKT) cells and inducing apoptosis through death receptors in cancer cells. It has been well established that the oncogenic signals of cancer cells are amplified by the overexpression of various membrane-bound receptors such as epidermal growth factor receptor (EGFR), vascular endothelial growth factor receptor (VEGFR), platelet-derived growth factor receptor (PDGFR) and insulin-like growth factor receptor (IGFR). Microbial amphiphiles, upon interaction with the cell membrane, are believed to suppress the activities of these cell surface receptors by fatty acid chain mediated membrane destabilization. This review analyzes the modes and mechanisms of action of these green molecules for application as potential anticancer agents.

Components of the CtBP1/BARS-dependent fission machinery

The brefeldin A ADP-ribosylated substrate, a member of the C-terminal-binding protein family that is referred to as CtBP1/BARS, is a dual-function protein that acts as a transcriptional co-repressor in the nucleus and as an inducer of membrane fission in the cytoplasm. In this review, we first discuss the mechanisms that enable CtBP1/BARS to shift between the nuclear transcriptional co-repressor and the cytosolic fission-inducing activities. Then, we focus on the role of CtBP1/BARS in membrane fission. CtBP1/BARS controls several fission events including macropinocytosis, fluid-phase endocytosis, COPI-coated vesicle formation, basolaterally directed post-Golgi carrier formation, and Golgi partitioning in mitosis. We report on recent advances in our understanding of the CtBP1/BARS membrane fission machineries that operate at the trans-side and at the cis-side of the Golgi complex. Specifically, we discuss how these machineries are assembled and regulated, and how they operate in the formation of the basolaterally directed post-Golgi carriers.

Production of mannosylerythritol lipids and their application in cosmetics

Mannosylerythritol lipids (MELs) are glycolipid biosurfactants abundantly produced by different basidiomycetous yeasts such as Pseudozyma, and show not only excellent interfacial properties but also versatile biochemical actions. These features of MELs make their application in new technology areas possible. Recently, the structural and functional variety of MELs was considerably expanded by advanced microbial screening methods. Different types of MELs bearing different hydrophilic and hydrophobic parts have been reported. The genes responsible for MEL biosynthesis were identified, and their genetic study is now in progress, aiming to control the chemical structure. The excellent properties leading to practical cosmetic ingredients, i.e., moisturization of dry skin, repair of damaged hair, activation of fibroblast and papilla cells and antioxidant and protective effects in skin cells, have been demonstrated on the yeast glycolipid biosurfactants. In this review, the current status of research and development on MELs, particularly the commercial application in cosmetics, is described.

Production and characterization of a glycolipid biosurfactant, mannosylerythritol lipid B, from sugarcane juice by Ustilago scitaminea NBRC 32730

Mannosylerythritol lipids (MELs) are glycolipid biosurfactants excreted by fungal strains. They show not only excellent surface-active properties but also versatile biochemical actions. Ustilago scitaminea NBRC 32730 has been reported mainly to produce a mono-acetylated and di-acylated MEL, MEL-B, from sucrose as sole carbon source. In order to make biosurfactant production more efficient, we focused our attention on the use of sugarcane juice, one of the most economical resources. The fungal strain produced MEL-B at the yield of 12.7 g/L from only sugarcane juice containing 22.4% w/w sugars. Supplementation with organic (yeast extract, peptone, and urea) and inorganic (sodium nitrate and ammonium nitrate) nitrogen sources markedly enhanced the production yield. Of the nitrogen sources, urea gave the best yield. Under optimum conditions, the strain produced 25.1 g/L of MEL-B from the juice (19.3% sugars) supplemented with 1 g/L of urea in a jar fermenter at 25 °C over 7 d. The critical micelle concentration (CMC) and the surface-tension at the CMC for the present MEL-B were 3.7×10(-6) M and 25.2 mN/m respectively. On water-penetration scan, the biosurfactant efficiently formed the lamella phase (L(α)) and myelins over a wide range of concentrations, indicating excellent surface-active and self-assembling properties. More significantly, the biosurfactant showed a ceramide-like skin-care property in a three-dimensional cultured human skin model. Thus, sugarcane juice is likely to be effective in glycolipid production by U. scitaminea NBRC 32730, and should facilitate the application of MELs.

Isolation of Pseudozyma churashimaensis sp. nov., a novel ustilaginomycetous yeast species as a producer of glycolipid biosurfactants, mannosylerythritol lipids

An ustilaginomycetous anamorphic yeast species isolated from the leaves of Saccharum officinarum (sugarcane) in Okinawa, Japan, was identified as a novel Pseudozyma species based on morphological and physiological aspects and molecular taxonomic analysis using the D1/D2 domains of the large subunit (26S) rRNA gene and the internal transcribed spacer 1 (ITS1)-5.8S-ITS2 regions. The name Pseudozyma churashimaensis sp. nov. was proposed for the novel species, with JCM 16988(T) as the type strain. Interestingly, P. churashimaensis was found to produce glycolipid biosurfactants, a mixture of mannosylerythritol lipids (MELs), including a novel tri-acetylated derivative (MEL-A2), from glucose. The observed critical micelle concentration (CMC) and the surface tension at CMC of MEL-A2 were 1.7 × 10⁻⁶ M and 29.2 mN/m, respectively. Moreover, on a water-penetration scan, MEL-A2 efficiently formed different lyotropic liquid crystalline phases, including the lamella phase at a wide range of concentrations, indicating its excellent surface-active and self-assembling properties. The novel strain of the genus Pseudozyma should thus facilitate the application of glycolipid biosurfactants in combination with other MEL producers.

Identification of the gene PaEMT1 for biosynthesis of mannosylerythritol lipids in the basidiomycetous yeast Pseudozyma antarctica

The yeast Pseudozyma antarctica produces a large amount of glycolipid biosurfactants known as mannosylerythritol lipids (MELs), which show not only excellent surface-active properties but also versatile biochemical actions. To investigate the biosynthesis of MELs in the yeast, we recently reported expressed sequence tag (EST) analysis and estimated genes expressing under MEL production conditions. Among the genes, a contiguous sequence of 938 bp, PA_004, showed high sequence identity to the gene emt1, encoding an erythritol/mannose transferase of Ustilago maydis, which is essential for MEL biosynthesis. The predicted translation product of the extended PA_004 containing the two introns and a stop codon was aligned with Emt1 of U. maydis. The predicted amino acid sequence shared high identity (72%) with Emt1 of U. maydis, although the amino-terminal was incomplete. To identify the gene as PaEMT1 encoding an erythritol/mannose transferase of P. antarctica, the gene-disrupted strain was developed by the method for targeted gene disruption, using hygromycin B resistance as the selection marker. The obtained ΔPaEMT1 strain failed to produce MELs, while its growth was the same as that of the parental strain. The additional mannosylerythritol into culture allowed ΔPaEMT1 strain to form MELs regardless of the carbon source supplied, indicating a defect of the erythritol/mannose transferase activity. Furthermore, we found that MEL formation is associated with the morphology and low-temperature tolerance of the yeast.

Activation of fibroblast and papilla cells by glycolipid biosurfactants, mannosylerythritol lipids

Mannosylerythritol lipids (MELs), the extracellular glycolipids produced from feedstock by yeasts belonging to the genus Pseudozyma, are the most promising biosurfactants known due to its versatile interfacial and biochemical actions. In order to broaden the application in cosmetics, the cell activating property of MELs was investigated using cultured fibroblast and papilla cells, and a three-dimensional cultured human skin model. The di-acetylated MEL (MEL-A) produced from soybean oil significantly increased the viability of the fibroblast cells over 150% compared with that of control cells. On the other hand, no cell activation was observed by the treatment with MEL-A produced from olive oil. The mono-acetylated MEL (MEL-B) hardly increased the cell viability. The viability of the fibroblast cells decreased with the addition of more than 1 microg/L of MELs, whereas the cultured human skin cells showed high viability with 5 microg/L of MELs. Interestingly, the papilla cells were dramatically activated with 0.001 microg/L of MEL-A produced from soybean oil: the cell viability reached at 150% compared with that of control cells. Consequently, the present MEL-A produced from soybean oil should have a potential as a new hair growth agent stimulating the papilla cells.

Biosurfactant-producing yeast isolated from Calyptogena soyoae (deep-sea cold-seep clam) in the deep sea

We describe a detailed structure determination of biosurfactant produced by Pseudozyma hubeiensis SY62, which was newly isolated from Calyptogena soyoae (deep-sea cold-seep clam, Shirouri-gai) at 1156 m in Sagami bay. P. hubeiensis SY62 was taxonomically slightly different from the P. hubeiensis type strain, which produces biosurfactants. Glycolipid production by the strain was also slightly different from those of previously reported strains. BS productivity was estimated to be around 30 g/l from the weight of the crude extract. At least five different spots of glycolipid biosurfactants (BSs) were detected by TLC. Results of nuclear magnetic resonance spectroscopies indicated the major product, namely MEL-C (4-O-[4'-O-acetyl-2',3'-di-O-alka(e)noil-beta-d-mannopyranosyl]-d-erythritol), as a promising BS. By further structural determination, the major fatty acids of MEL-C were estimated to be saturated C(6), C(10), and C(12) acids, which were shorter than those of previously reported MEL-C. Furthermore, (1)H-NMR spectra implied the presence of C(2) acids as acyl groups. According to surface tension determination, the novel MEL-C showed larger critical micelle concentration (1.1x10(-5) M) than conventional MEL-C which bound C(10) and C(12) acids (9.1x10(-6) M). From these results, shorter fatty acids would confer hydrophilicity onto the novel MEL-C.

Mannosylerythritol lipids: a review

Mannosylerythritol lipids (MELs) are surface active compounds that belong to the glycolipid class of biosurfactants (BSs). MELs are produced by Pseudozyma sp. as a major component while Ustilago sp. produces them as a minor component. Although MELs have been known for over five decades, they recently regained attention due to their environmental compatibility, mild production conditions, structural diversity, self-assembling properties and versatile biochemical functions. In this review, the MEL producing microorganisms, the production conditions, their applications, their diverse structures and self-assembling properties are discussed. The biosynthetic pathways and the regulatory mechanisms involved in the production of MEL are also explained here.

Guanosine promotes B16F10 melanoma cell differentiation through PKC-ERK 1/2 pathway

Malignant melanoma is one of the most lethal cancers. Nowadays, several anti-melanoma therapies have been employed. However, the poor prognosis and/or the increased toxicity of those treatments clearly demonstrate the requirement of searching for new drugs or novel combined chemotherapeutic protocols, contemplating both effectiveness and low toxicity. Guanosine (Guo) has been used in combination with acriflavina to potentiate the latter's antitumor activity, through still unknown mechanisms. Here, we show that Guo induces B16F10 melanoma cell differentiation, attested by growth arrest, dendrite-like outgrowth and increased melanogenesis, and also reduced motility. A sustained ERK 1/2 phosphorylation was observed after Guo treatment and ERK inhibition led to blockage of dendritogenesis. Intracellular cyclic AMP was not involved in ERK activation, since its levels remained unchanged. Protein kinase C (PKC), in contrast to phospholipase C (PLC), inhibition completely prevented ERK activation. While the classical melanoma differentiation agent forskolin activates cAMP-PKA-Raf-MEK-ERK pathway in B16F10 cells, here we suggest that a cAMP-independent, PKC-ERK axis is involved in Guo-induced B16F10 differentiation. Altogether, our results show that Guo acts as a differentiating agent, with cytostatic rather than cytotoxic properties, leading to a decreased melanoma malignancy. Thus, we propose that Guo may be envisaged in combination with lower doses of conventional anti-melanoma drugs, in an attempt to prevent or diminish their adverse effects.

Differentiation-inducing activity of lupane triterpenes on a mouse melanoma cell line

Lupane triterpenes were found to promote melanogenesis, a hallmark of B16 2F2 mouse melanoma cell differentiation. Studies of the structure-activity relationships demonstrated that the keto function at C-3 of the lupane skeleton played important roles in the melanogenic activities of lupane triterpenes on melanoma cells. The carbonyl group at C-17 of lupane triterpenes was essential against their apoptosis-inducing activity against human cancer cells via the inhibition of topoisomerase I. We investigated whether signaling mechanisms were involved in the stimulative effects of lupane triterpenes on the melanogenesis of B16 2F2 cells. In experiments using selective inhibitors against various signal transduction molecules and Western blotting analysis, it was suggested that p38 MAPK was involved in melanoma cell differentiation as a downstream effector of PKA. Lupeol (compound 1), a lupane triterpene, induced dendrite formations, a morphological hallmark of B16 2F2 cell differentiation by rearrangement of the actin cytoskeleton. The activation of cofilin, an actin depolymerizing factor, by compound 1 caused actin fiber disassembly in B16 2F2 cells. Furthermore, compound 1 was shown to inhibit the cell motilities of human melanoma and neuroblastoma in vitro.

Protein kinase C in melanoma

Protein kinase C (PKC) is activated by diacylglycerol generated by receptor-mediated hydrolysis of membrane phospholipids to mediate signals for cell growth and plays as a target of tumor-promoting phorbol esters in malignant transformation. PKC is a family of enzymes and their expression profiles have been examined in the normal melanocytes and melanoma cells, and studies have been carried out on the functions of PKC isoforms in proliferation, transformation, and metastasis of melanoma cells. Here, we summarize current knowledge of the expression and possible roles of the PKC family in melanoma in comparison with those of normal melanocytes.

The role of protein kinase C-alpha (PKC-alpha) in melanoma

In the 1980s, protein kinase C (PKC) was identified as a contributing factor in skin tumorigenesis. As drugs targeting specifically PKC have become available, the intent of this review was to assess the role of PKC, in particular of PKC-alpha in melanoma or other skin cancers. We reviewed and summarized published studies examining the role of PKC-alpha in the development of melanoma or other skin cancers. Most studies to date have been cell-culture based. In models of melanoma, PKC-alpha activation is typically associated with increased tumour cell proliferation, invasiveness and decreased differentiation, suggesting that PKC-alpha inhibitors, such as aprinocarsen, an antisense oligonucleotide directed against PKC-alpha, may be appropriate in the treatment of skin malignancies. Because of the recent developments on selective or specific PKC-alpha inhibitors, including aprinocarsen, there is a growing need to conduct further translational research, especially in melanoma patients, to identify the patient population that might benefit most from PKC-alpha targeted therapy.

Novel p21-activated kinase-dependent protrusions characteristically formed at the edge of transformed cells

During long-term culture, certain lines become neoplastic while accumulating changes in cell shape. Early and late cell populations have characteristic shape phenotypes that have been quantified by computerized assay. Phenotypes are determined from variables describing three-dimensional aspects of the subcellular distribution of mass. The features of cells can be recognized by use of latent factors, which are theoretical variables based on the covariance of the primary variables. Factor #7 represented a cell edge feature different from filopodia. We studied the morphological characteristics and morphogenesis of the feature. Brief exposure of cells from rat tracheal epithelium to phorbol 12-myristate 13-acetate (PMA) enhanced #7 values. The time to reach maximal #7 values was prolonged if PMA was administered with calcium ionophore or lysophosphatidic acid (LPA). Factor #7 was elevated during periods of ruffling suppression and stress fiber reorganization. Cells showing high #7 values were examined by scanning electron microscopy (SEM) and found to exhibit strap-shaped and cupola-shaped projections. Because RhoA regulates stress fiber formation, we sought to perturb #7 features by introducing dominant-acting negative and positive constructs of RhoA, RhoA-N19, and RhoA-V14. Neither affected #7 values. Although overexpression of the kinase inhibitory domain of p21-activated kinase 1 (PAK) had no effect on #7 values, they were affected by overexpression of a domain binding PAK-interacting guanine nucleotide exchange factor (PIX). Because a PAK-PIX complex is implicated in the remodeling of focal complexes (FCs) and recycling of PAK to the cytoplasm, the results implicate a component of FCs in the formation of #7 features. The data suggested that feature formation is driven by activated Cdc42-binding kinase (ACK) and Rac. Moreover, they suggested that the #7 protrusions are neurite-like structures and that their development involves FC regulation.

Mannosylerythritol lipids, yeast glycolipid biosurfactants, are potential affinity ligand materials for human immunoglobulin G

Three mannosylerythritol lipids (MEL-A, -B, and -C), yeast glycolipid biosurfactants, were independently attached to poly (2-hydroxyethyl methacrylate) beads (PHEMA), and the three obtained MEL-PHEMA composites were examined for their binding affinity to human immunoglobulin G (HIgG). Of the three composites, the composite bearing MEL-A exhibited the highest binding capacity for HIgG. The binding amount of HIgG increased with increased applied concentration, reaching 106 mg HIgG (per g of composite), with a binding yield of 81%. Interestingly, the protein binding to the composite appeared to follow two different modes (Langmuir type and Freundlich type) depending on the applied concentration. The binding amount of human serum albumin to the composite was much smaller than that of HIgG. The bound human serum albumin, however, had minimal effect on the subsequent binding of HIgG, indicating that the two proteins have different binding sites onto the composite. More significantly, the bound HIgG was efficiently recovered under significantly mild elution conditions: Approximately 90% of the protein was eluted from the composite with phosphate buffer at pH 7. These results indicate that the glycolipid biosurfactant may have great potential as an affinity ligand material for HIgG.