Chromophore-assisted light inactivation of pKi-67 leads to inhibition of ribosomal RNA synthesis

OBJECTIVES

Expression of the nuclear Ki-67 protein (pKi-67) is strongly associated with cell proliferation. For this reason, antibodies against this protein are widely used as prognostic tools for the assessment of cell proliferation in biopsies from cancer patients. Despite this broad application in histopathology, functional evidence for the physiological role of pKi-67 is still missing. Recently, we proposed a function of pKi-67 in the early steps of ribosomal RNA (rRNA) synthesis. Here, we have examined the involvement of pKi-67 in this process by photochemical inhibition using chromophore-assisted light inactivation (CALI).

MATERIALS AND METHODS

Anti-pKi-67 antibodies were labelled with the fluorochrome fluorescein 5(6)-isothiocyanate and were irradiated after binding to their target protein.

RESULTS

Performing CALI in vitro on cell lysates led to specific cross-linking of pKi-67. Moreover, the upstream binding factor (UBF) necessary for rRNA transcription was also partly subjected to cross-link formation, indicating a close spatial proximity of UBF and pKi-67. CALI in living cells, using micro-injected antibody, caused a striking relocalization of UBF from foci within the nucleoli to spots located at the nucleolar rim or within the nucleoplasm. pKi-67-CALI resulted in dramatic inhibition of RNA polymerase I-dependent nucleolar rRNA synthesis, whereas RNA polymerase II-dependent nucleoplasmic RNA synthesis remained almost unaltered.

CONCLUSIONS

Our data presented here argue for a crucial role of pKi-67 in RNA polymerase I-dependent nucleolar rRNA synthesis.

Molecular characterization of a Theileria lestoquardi gene encoding for immunogenic protein splice variants

A Theileria lestoquardi schizont cDNA library was screened using sera collected from sheep recovering from a natural malignant theileriosis infection. An immunogenic clone (clone-5) was isolated and its full sequence was obtained using rapid amplification of cDNA ends polymerase chain reaction (PCR) technique. PCR experiments and sequencing demonstrated the presence of two transcript forms of the gene, resulting from splicing variation at the single intron found in the gene. Both gene products, clone-5 long and clone-5 short variants with calculated molecular weights of 99.9 and 72.7 kDa, respectively, were expressed in a T. lestoquardi-infected cell line. BLAST searches suggested the presence of homologues of the gene in both the Theileria parva and Theileria annulata genomes, with identities of 53 and 62% on the DNA level, respectively. The intron was preserved in size, sequence, and location within the gene in these parasites. Analysis of the subcellular localization of the clone-5 proteins showed a predominant parasite membrane association in T. lestoquardi-infected cells. Both recombinantly produced forms were found to be reactive with sera from infected animals. Bioinformatic analyses were employed to address the possible function of the gene products in the biology of T. lestoquardi.

The expression of Ki-67, MCM3, and p27 defines distinct subsets of proliferating, resting, and differentiated cells

The mini-chromosome maintenance proteins (MCM), which are involved in the control of DNA replication, and the cyclin-dependent kinase inhibitors, such as p27/KIP1, represent two groups of proteins that are currently under investigation as diagnostic tumour markers. The expression of p27 and MCM3 was compared with the expression of the Ki-67 protein, an approved marker for proliferating cells, extensively used in histopathology and cancer research. The expression pattern of all three proteins was assessed on germinal centres and oral mucosa, which display a well-defined spatio-temporal organization. The expression of the p27 protein was closely related to differentiated cells, whereas MCM3 and Ki-67 were predominantly localized to the regions of proliferating cells. However, it is important to note that considerable numbers of cells that were growth-arrested, as confirmed by the absence of the Ki-67 protein, stained positive for the MCM3 protein. These results were verified in vitro using growth-arrested Swiss 3T3. The MCM3 protein is therefore expressed in cells that have ceased to proliferate, but are not terminally differentiated, according to the absence of p27 protein expression. In conclusion, a combined analysis of Ki-67, MCM3, and p27 protein expression may provide a more detailed insight into the cell proliferation and differentiation processes that determine individual tumour growth.

The Ki-67 protein: from the known and the unknown

The expression of the human Ki-67 protein is strictly associated with cell proliferation. During interphase, the antigen can be exclusively detected within the nucleus, whereas in mitosis most of the protein is relocated to the surface of the chromosomes. The fact that the Ki-67 protein is present during all active phases of the cell cycle (G(1), S, G(2), and mitosis), but is absent from resting cells (G(0)), makes it an excellent marker for determining the so-called growth fraction of a given cell population. In the first part of this study, the term proliferation marker is discussed and examples of the applications of anti-Ki-67 protein antibodies in diagnostics of human tumors are given. The fraction of Ki-67-positive tumor cells (the Ki-67 labeling index) is often correlated with the clinical course of the disease. The best-studied examples in this context are carcinomas of the prostate and the breast. For these types of tumors, the prognostic value for survival and tumor recurrence has repeatedly been proven in uni- and multivariate analysis. The preparation of new monoclonal antibodies that react with the Ki-67 equivalent protein from rodents now extends the use of the Ki-67 protein as a proliferation marker to laboratory animals that are routinely used in basic research. The second part of this review focuses on the biology of the Ki-67 protein. Our current knowledge of the Ki-67 gene and protein structure, mRNA splicing, expression, and cellular localization during the cell-division cycle is summarized and discussed. Although the Ki-67 protein is well characterized on the molecular level and extensively used as a proliferation marker, the functional significance still remains unclear. There are indications, however, that Ki-67 protein expression is an absolute requirement for progression through the cell-division cycle.

The Ki-67 protein: from the known and the unknown

The expression of the human Ki-67 protein is strictly associated with cell proliferation. During interphase, the antigen can be exclusively detected within the nucleus, whereas in mitosis most of the protein is relocated to the surface of the chromosomes. The fact that the Ki-67 protein is present during all active phases of the cell cycle (G(1), S, G(2), and mitosis), but is absent from resting cells (G(0)), makes it an excellent marker for determining the so-called growth fraction of a given cell population. In the first part of this study, the term proliferation marker is discussed and examples of the applications of anti-Ki-67 protein antibodies in diagnostics of human tumors are given. The fraction of Ki-67-positive tumor cells (the Ki-67 labeling index) is often correlated with the clinical course of the disease. The best-studied examples in this context are carcinomas of the prostate and the breast. For these types of tumors, the prognostic value for survival and tumor recurrence has repeatedly been proven in uni- and multivariate analysis. The preparation of new monoclonal antibodies that react with the Ki-67 equivalent protein from rodents now extends the use of the Ki-67 protein as a proliferation marker to laboratory animals that are routinely used in basic research. The second part of this review focuses on the biology of the Ki-67 protein. Our current knowledge of the Ki-67 gene and protein structure, mRNA splicing, expression, and cellular localization during the cell-division cycle is summarized and discussed. Although the Ki-67 protein is well characterized on the molecular level and extensively used as a proliferation marker, the functional significance still remains unclear. There are indications, however, that Ki-67 protein expression is an absolute requirement for progression through the cell-division cycle.

The Ki-67 protein: from the known and the unknown

The expression of the human Ki-67 protein is strictly associated with cell proliferation. During interphase, the antigen can be exclusively detected within the nucleus, whereas in mitosis most of the protein is relocated to the surface of the chromosomes. The fact that the Ki-67 protein is present during all active phases of the cell cycle (G(1), S, G(2), and mitosis), but is absent from resting cells (G(0)), makes it an excellent marker for determining the so-called growth fraction of a given cell population. In the first part of this study, the term proliferation marker is discussed and examples of the applications of anti-Ki-67 protein antibodies in diagnostics of human tumors are given. The fraction of Ki-67-positive tumor cells (the Ki-67 labeling index) is often correlated with the clinical course of the disease. The best-studied examples in this context are carcinomas of the prostate and the breast. For these types of tumors, the prognostic value for survival and tumor recurrence has repeatedly been proven in uni- and multivariate analysis. The preparation of new monoclonal antibodies that react with the Ki-67 equivalent protein from rodents now extends the use of the Ki-67 protein as a proliferation marker to laboratory animals that are routinely used in basic research. The second part of this review focuses on the biology of the Ki-67 protein. Our current knowledge of the Ki-67 gene and protein structure, mRNA splicing, expression, and cellular localization during the cell-division cycle is summarized and discussed. Although the Ki-67 protein is well characterized on the molecular level and extensively used as a proliferation marker, the functional significance still remains unclear. There are indications, however, that Ki-67 protein expression is an absolute requirement for progression through the cell-division cycle.

The Ki-67 protein: from the known and the unknown

The expression of the human Ki-67 protein is strictly associated with cell proliferation. During interphase, the antigen can be exclusively detected within the nucleus, whereas in mitosis most of the protein is relocated to the surface of the chromosomes. The fact that the Ki-67 protein is present during all active phases of the cell cycle (G(1), S, G(2), and mitosis), but is absent from resting cells (G(0)), makes it an excellent marker for determining the so-called growth fraction of a given cell population. In the first part of this study, the term proliferation marker is discussed and examples of the applications of anti-Ki-67 protein antibodies in diagnostics of human tumors are given. The fraction of Ki-67-positive tumor cells (the Ki-67 labeling index) is often correlated with the clinical course of the disease. The best-studied examples in this context are carcinomas of the prostate and the breast. For these types of tumors, the prognostic value for survival and tumor recurrence has repeatedly been proven in uni- and multivariate analysis. The preparation of new monoclonal antibodies that react with the Ki-67 equivalent protein from rodents now extends the use of the Ki-67 protein as a proliferation marker to laboratory animals that are routinely used in basic research. The second part of this review focuses on the biology of the Ki-67 protein. Our current knowledge of the Ki-67 gene and protein structure, mRNA splicing, expression, and cellular localization during the cell-division cycle is summarized and discussed. Although the Ki-67 protein is well characterized on the molecular level and extensively used as a proliferation marker, the functional significance still remains unclear. There are indications, however, that Ki-67 protein expression is an absolute requirement for progression through the cell-division cycle.

The Ki-67 protein: from the known and the unknown

The expression of the human Ki-67 protein is strictly associated with cell proliferation. During interphase, the antigen can be exclusively detected within the nucleus, whereas in mitosis most of the protein is relocated to the surface of the chromosomes. The fact that the Ki-67 protein is present during all active phases of the cell cycle (G(1), S, G(2), and mitosis), but is absent from resting cells (G(0)), makes it an excellent marker for determining the so-called growth fraction of a given cell population. In the first part of this study, the term proliferation marker is discussed and examples of the applications of anti-Ki-67 protein antibodies in diagnostics of human tumors are given. The fraction of Ki-67-positive tumor cells (the Ki-67 labeling index) is often correlated with the clinical course of the disease. The best-studied examples in this context are carcinomas of the prostate and the breast. For these types of tumors, the prognostic value for survival and tumor recurrence has repeatedly been proven in uni- and multivariate analysis. The preparation of new monoclonal antibodies that react with the Ki-67 equivalent protein from rodents now extends the use of the Ki-67 protein as a proliferation marker to laboratory animals that are routinely used in basic research. The second part of this review focuses on the biology of the Ki-67 protein. Our current knowledge of the Ki-67 gene and protein structure, mRNA splicing, expression, and cellular localization during the cell-division cycle is summarized and discussed. Although the Ki-67 protein is well characterized on the molecular level and extensively used as a proliferation marker, the functional significance still remains unclear. There are indications, however, that Ki-67 protein expression is an absolute requirement for progression through the cell-division cycle.

The Ki-67 protein: from the known and the unknown

The expression of the human Ki-67 protein is strictly associated with cell proliferation. During interphase, the antigen can be exclusively detected within the nucleus, whereas in mitosis most of the protein is relocated to the surface of the chromosomes. The fact that the Ki-67 protein is present during all active phases of the cell cycle (G(1), S, G(2), and mitosis), but is absent from resting cells (G(0)), makes it an excellent marker for determining the so-called growth fraction of a given cell population. In the first part of this study, the term proliferation marker is discussed and examples of the applications of anti-Ki-67 protein antibodies in diagnostics of human tumors are given. The fraction of Ki-67-positive tumor cells (the Ki-67 labeling index) is often correlated with the clinical course of the disease. The best-studied examples in this context are carcinomas of the prostate and the breast. For these types of tumors, the prognostic value for survival and tumor recurrence has repeatedly been proven in uni- and multivariate analysis. The preparation of new monoclonal antibodies that react with the Ki-67 equivalent protein from rodents now extends the use of the Ki-67 protein as a proliferation marker to laboratory animals that are routinely used in basic research. The second part of this review focuses on the biology of the Ki-67 protein. Our current knowledge of the Ki-67 gene and protein structure, mRNA splicing, expression, and cellular localization during the cell-division cycle is summarized and discussed. Although the Ki-67 protein is well characterized on the molecular level and extensively used as a proliferation marker, the functional significance still remains unclear. There are indications, however, that Ki-67 protein expression is an absolute requirement for progression through the cell-division cycle.

Molecular basis of the alpha-MSH/IL-1 antagonism

The neuropeptide alpha-melanocyte stimulating hormone (alpha-MSH) is recognized as a potent mediator of immune and inflammatory reactions. Accordingly, alpha-MSH in vitro, as well as in vivo, antagonizes the proinflammatory activities of cytokines such as interleukin-1 (IL-1), IL-6, and tumor necrosis factor alpha (TNF alpha). Since the molecular basis of these antiinflammatory effects is not well known, the influence of alpha-MSH on IL-1 beta-induced chemokine production and transcription factor activation was investigated in human keratinocytes. alpha-MSH, in a dose-dependent manner, after 48 h, significantly reduced the IL-1 beta mediated secretion of the C-X-C chemokines IL-8 and Gro alpha. This was confirmed by semiquantitative RT-PCR, which revealed a marked down-regulation in IL-8 and Gro alpha mRNA expression. Furthermore, we determined the effect of alpha-MSH on the IL-1 beta-induced activation of the nuclear factor kappa B (NF kappa B)--a major transcription factor for chemokine genes. Electrophoretic mobility-shift-assays showed that alpha-MSH, in a dose range from 10(-6) to 10(-12) M, significantly downregulated the IL-1 beta-induced activation of NF kappa B 10 minutes after stimulation. Therefore, NF kappa B inactivation by alpha-MSH appears to be a crucial event, one that is responsible for the downregulation of cytokine gene transcription.

Mechanisms of the antiinflammatory effects of alpha-MSH. Role of transcription factor NF-kappa B and adhesion molecule expression

The recruitment of leukocytes from the circulation to inflamed tissue is regulated by the expression of adhesion molecules on both leukocytes and endothelial cells. The proopiomelanocortin-derived peptide alpha-melanocyte stimulating hormone (alpha-MSH) is known to modulate inflammation. Thus, we investigated the influence of alpha-MSH on the LPS-induced expression of the adhesion molecules E-selectin and VCAM-1 on endothelial cells. Human microvascular endothelial cells (HMEC-1) were treated with LPS (100 ng/ml) alone or in the presence of alpha-MSH (10(-8) to 10(-16) M). RT-PCR analysis showed that alpha-MSH significantly reduced LPS-induced expression of VCAM-1 and E-selectin. Since many adhesion molecules contain regulatory NF-kappa B sites in their promoter region, the role of alpha-MSH in the activation of the transcription factor NF-alpha B was also investigated. alpha-MSH significantly downregulated the LPS-mediated activation of NF-kappa B, in a dose-dependent manner. These findings indicate that modulation of the transcription factor NF-kappa B is a crucial molecular event, one that seems to be responsible for the antiinflammatory effects of alpha-MSH.

Role of epidermal cell-derived alpha-melanocyte stimulating hormone in ultraviolet light mediated local immunosuppression

Irradiation of the skin with ultraviolet light (UV) results in profound alterations of both local and systemic immune responses. These effects are largely mediated by soluble mediators released from epidermal cells in response to UV. It is well known that keratinocytes release increased amounts of cytokines upon UV-irradiation. UV-light also induces the release of the proopiomelanocortin (POMC)-derived peptide, alpha-melanocyte-stimulating hormone (alpha MSH), from keratinocytes, and upregulates the expression of POMC mRNA. alpha MSH exerts a variety of immunomodulating and antiinflammatory effects, mainly by virtue of its capacity to alter the function of antigen presenting cells and vascular endothelial cells. Within an in vivo mouse-model, both intravenous and topical application of alpha MSH resulted in inhibiting the induction, eliciting a contact hypersensitivity reaction, and inducing hapten-specific tolerance. These findings indicate that alpha MSH, released in the epidermis after UV irradiation, may contribute to UV-mediated immunosuppression. The therapeutic application of alpha MSH or alpha MSH-derived peptides may prove to be a useful approach for treating inflammatory skin diseases.

A nonspecific, single-stranded nuclease activity with characteristics of a topoisomerase found in a major grass pollen allergen: possible biological significance

The major allergen from timothy grass pollen, Phlp5b (Phleum pratense), was shown to exhibit ribonuclease activity. It turned out that the C-terminal portion of this molecule was the biologically active domain. Here evidence is presented that the allergen is a single-stranded, sugar-nonspecific nuclease with topoisomerase activity. An isomerase-specific active site was identified, and a non-active mutant was constructed by site directed mutagenesis, and showed no nucleolytic activity. In contrast to the wild type (WT), the mutant did not dimerize. Although the binding capacity of IgE antibodies toward the mutant was reduced as compared to the WT, the allergenic activity was retained. We conclude that the allergen Phlp5b is a single-stranded nuclease with an unusual topoisomerase-like activity. This biological activity is not by itself connected to the allergenicity of the molecule. Whether the enzymatic activity is responsible for the induction of the allergic sensitization and inflammation remains an open question.

Extracellular matrix regulates steady-state mRNA levels of the proliferation associated protein Ki-67 in endometrial cancer cells

We investigated whether components of the extracellular matrix have the potential to regulate the proliferative activity of endometrial adenocarcinoma cells. Culturing of cells on the reconstituted basement membrane matrigel down-regulated the steady-state mRNA levels of the proliferation associated protein, Ki-67, in the endometrial adenocarcinoma cell lines HEC 1B(L) and Ishikawa after 48-96 h of culture on the matrix substrate. Proliferation of Ishikawa was stimulated again if cells were cultured on matrigel and challenged by proteins representing functional domains of tenascin-C, a mesenchymal glycoprotein. The fibronectin-type-III-like repeats 6-8 of tenascin-C were found to be the most potent. In summary, evidence is provided that components of both epithelial and stromal extracellular matrices can function as regulators of cell growth.

Ultraviolet light and interleukin-10 modulate expression of cytokines by transformed human dermal microvascular endothelial cells (HMEC-1)

Exposure of the skin to ultraviolet (UV) light causes DNA damage, inflammation, and impairment of local as well as systemic immune responses. Dermal microvascular endothelial cells are key elements for the recruitment of inflammatory cells during the pathogenesis of inflammatory skin diseases via the expression of adhesion molecules and the release of cytokines. Because UVB may directly affect the function of dermal cells it was investigated whether UVB irradiation alters the production of proinflammatory and chemotactic cytokines by endothelial cells. UVB exposure of transformed human microvascular endothelial cells (HMEC-1) resulted in a dose dependently increased mRNA expression as well as release of interleukin (IL)-1beta, IL-6, IL-8, and growth-regulated oncogene alpha (GROalpha). Maximum cytokine production was observed 16-24 h after irradiation when 7.5-12.5 mJ UVB per cm2 were used. In addition, it was examined whether IL-10, which is upregulated in keratinocytes following UVB irradiation and accounts for UV mediated immunosuppression such as inhibition of contact hypersensitivity, also affects endothelial cell cytokine production. Treatment of HMEC-1 with IL-10 significantly enhanced IL-6 and IL-8 release and further upregulated UVB-induced IL-6 and IL-8 mRNA expression. These findings demonstrate that UVB both directly and indirectly via the release of IL-10 stimulates microvascular endothelial cells to produce proinflammatory cytokines and chemokines that are required for the migration and activation of inflammatory cells in UV-mediated inflammatory skin reactions.

Cutaneous immunomodulation and coordination of skin stress responses by alpha-melanocyte-stimulating hormone

The capacity of the skin immune system to mount various types of immune responses is largely dependent on their ability to release and respond to different signals provided by immunoregulatory mediators such as cytokines. There is recent evidence that neuropeptides such as alpha-melanocyte-stimulating hormone (alpha MSH), upon stimulation, are released by epidermal cells including keratinocytes, Langerhans cells, and melanocytes as well as immunocompetent cells. Moreover, alpha MSH recently has been recognized as a potent immunomodulating agent, which inhibits the production and activity of immunoregulatory and proinflammatory cytokines such as IL-1, IL-2, interferon-gamma, downregulates the expression of costimulatory molecules (B7) on antigen-presenting cells; and recently turned out to be a potent inducer of inhibitory mediators such as cytokine synthesis inhibitory factor interleukin-10. Recently, it also was discovered that monocytes among the five known melanocortin (MC) receptors only express MC-1, which is specific for alpha MSH. The expression of MC-1 on monocytes is upregulated by mitogens, endotoxins, and proinflammatory cytokines. There is also recent evidence for the in vivo relevance of the immunosuppressing capacity of alpha MSH. Accordingly, in animals alpha MSH has been shown to inhibit the induction of contact hypersensitivity reactions and to induce hapten-specific tolerance. These findings indicate that, in addition to the cytokine network, neurohormones within the cutaneous microenvironment are a crucial element for the induction, elicitation, and regulation of cutaneous immune and inflammatory responses.

Neuropeptides in the skin: interactions between the neuroendocrine and the skin immune systems

The interaction between components of the nervous system and multiple target cells in the cutaneous immune system has been receiving increasing attention. It has been observed that certain skin diseases such as psoriasis and atopic dermatitis have a neurogenic component. Neuropeptides released by sensory nerves that innervate the skin and often contact epidermal and dermal cells can directly modulate functions of keratinocytes, Langerhans cells (LC), mast cells, dermal microvascular endothelial cells and infiltrating immune cells. Among these neuropeptides the tachykinins substance P (SP) and neurokinin A (NKA), calcitonin gene-related peptide (CGRP), vasoactive intestinal peptide (VIP) and somatostatin (SOM) have been reported to effectively modulate skin and immune cell functions such as cell proliferation, cytokine production or antigen presentation under physiological or pathophysiological conditions. Expression and regulation of their corresponding receptors that are expressed on a variety of skin cells as well as the presence of neuropeptide-specific peptidases such as neutral endopeptidase (NEP) or angiotensin-converting enzyme (ACE) determine the final biological response mediated by these peptides on the target cell or tissue. Likewise, skin cells like keratinocytes or fibroblasts are a source for neurotrophins such as nerve growth factor that are required not only for survival and regeneration of sensory neurons but also to control responsiveness of these neurons to external stimuli. Therefore, neuropeptides, neuropeptide receptors, neuropeptide-degrading enzymes and neurotrophins participate in a complex, interdependent network of mediators that modulate skin inflammation, wound healing and the skin immune system. This review will focus on recent studies demonstrating the role of tachykinins, CGRP, SOM and VIP and their receptors and neuropeptide-degrading enzymes in mediating neurogenic inflammation in the skin.

Ki-67 expression during rat liver regeneration after partial hepatectomy

Antibodies to the cell-cycle-associated Ki-67 protein have been widely used for more than a decade as markers of proliferative cells. The prototype antibody Ki-67 reacted only with snap-frozen human tissue, but a novel antibody, MIB-1, was able to detect the Ki-67 antigen in paraffin wax-embedded human tissue. The ability of MIB-5, a novel antibody reactive with the rat equivalent Ki-67 protein, to immunohistochemically detect cycling parenchymal and littoral cells in the regenerating rat liver is reported. Rats underwent a standard two-thirds partial hepatectomy (PH), and groups of three animals were killed at intervals for up to 192 hours after PH. DNA synthesis was monitored by flash labeling with bromodeoxyuridine, and the response was as expected with a significant upsurge in hepatocyte labeling at 16 to 17 hours after PH. On the other hand, MIB-5 labeled a relatively constant percentage of hepatocytes (4%-8%) during the first 16 hours after PH, before a large proportion became labeled, also at 17 hours. The temporal pattern of MIB-5 labeling was similar to that of bromodeoxyuridine labeling, although, as expected, MIB-5 indices were higher. Semiquantification of Ki-67 messenger RNA (mRNA) levels by reverse-transcription polymerase chain reaction showed modest (fourfold to fivefold) increases in abundance during the first 12 hours after PH, but then levels increased dramatically to be at least 15-fold those of intact liver at 36 hours after PH. Much higher than normal levels of Ki-67 mRNA persisted throughout the period of study and even at 96 hours after PH they were still ninefold greater than normal. This study has shown the usefulness of the MIB-5 antibody to monitor proliferation in the rat liver, and furthermore, the pattern of expression of both the mRNA and the protein suggest that the Ki-67 protein, with hitherto unknown function, is more abundant in DNA synthesis and mitosis than in the early or even very late first G1 phase.

Human dermal microvascular endothelial cells express the melanocortin receptor type 1 and produce increased levels of IL-8 upon stimulation with alpha-melanocyte-stimulating hormone

Pro-opiomelanocortin (POMC)-derived peptides such as alpha-melanocyte-stimulating hormone (alpha-MSH) recently have been recognized as mediators with potent immunomodulating and anti-inflammatory properties. Their effects are mediated via different protein G-coupled melanocortin (MC) receptors that are capable to bind one or more POMC-derived peptides. Among these receptors, MC-1 is specific for alpha-MSH and adrenocorticotropin. The purpose of the present study was to investigate whether MC receptors are expressed on normal human dermal microvascular endothelial cells (HDMEC) as well as transformed human dermal microvascular endothelial cells (HMEC-1). Using semiquantitative reverse transcriptase-PCR and MC receptor-specific primers, both HDMEC and HMEC-1 were found to express MC-1 constitutively. In addition, MC-1 expression was increased upon stimulation with IL-1beta or alpha-MSH itself. Other known MC receptors were neither detectable in unstimulated nor in IL-1beta- or alpha-MSH-stimulated cells. The binding of alpha-MSH by HMEC-1 was specific and saturable as demonstrated by competitive and saturation-binding studies with 125I-labeled alpha-MSH (Kd: 1.1 nM). To evaluate the physiologic relevance of MC-1 expression, HMEC-1 were treated with various concentrations of alpha-MSH (10(-15)-10(-6) M) and were investigated for their cytokine-producing capacity. Alpha-MSH (10(-10)-10(-8) M) significantly up-regulated IL-8 release and mRNA expression by HMEC-1. In contrast, the production of IL-1 or IL-6 by HMEC-1 was not affected upon treatment with alpha-MSH. These data provide first evidence that HDMEC express functional MC receptors. Therefore, alpha-MSH, which is released in the skin during cutaneous inflammation via inducing chemokines may represent an important signal required for leukocyte-endothelial cell interaction.

Human dermal microvascular endothelial cells express the melanocortin receptor type 1 and produce increased levels of IL-8 upon stimulation with alpha-melanocyte-stimulating hormone

Pro-opiomelanocortin (POMC)-derived peptides such as alpha-melanocyte-stimulating hormone (alpha-MSH) recently have been recognized as mediators with potent immunomodulating and anti-inflammatory properties. Their effects are mediated via different protein G-coupled melanocortin (MC) receptors that are capable to bind one or more POMC-derived peptides. Among these receptors, MC-1 is specific for alpha-MSH and adrenocorticotropin. The purpose of the present study was to investigate whether MC receptors are expressed on normal human dermal microvascular endothelial cells (HDMEC) as well as transformed human dermal microvascular endothelial cells (HMEC-1). Using semiquantitative reverse transcriptase-PCR and MC receptor-specific primers, both HDMEC and HMEC-1 were found to express MC-1 constitutively. In addition, MC-1 expression was increased upon stimulation with IL-1beta or alpha-MSH itself. Other known MC receptors were neither detectable in unstimulated nor in IL-1beta- or alpha-MSH-stimulated cells. The binding of alpha-MSH by HMEC-1 was specific and saturable as demonstrated by competitive and saturation-binding studies with 125I-labeled alpha-MSH (Kd: 1.1 nM). To evaluate the physiologic relevance of MC-1 expression, HMEC-1 were treated with various concentrations of alpha-MSH (10(-15)-10(-6) M) and were investigated for their cytokine-producing capacity. Alpha-MSH (10(-10)-10(-8) M) significantly up-regulated IL-8 release and mRNA expression by HMEC-1. In contrast, the production of IL-1 or IL-6 by HMEC-1 was not affected upon treatment with alpha-MSH. These data provide first evidence that HDMEC express functional MC receptors. Therefore, alpha-MSH, which is released in the skin during cutaneous inflammation via inducing chemokines may represent an important signal required for leukocyte-endothelial cell interaction.

The role of alpha-melanocyte-stimulating hormone in cutaneous biology

alpha-Melanocyte stimulating hormone is a neuroimmunomodulating peptide that was recently detected in many non-pituitary tissues including the skin. Accordingly, epidermal cells such as keratinocytes and melanocytes (as well as dermal cells such as fibroblasts and endothelial cells), after stimulation with pro-inflammatory cytokines or UV light, synthesize, and release alpha MSH. The effects of these peptides are mediated through specific melanocortin (MC) receptors that can be detected on immunocompetent and inflammatory cells as well as on keratinocytes, melanocytes, fibroblasts, and endothelial cells. In addition to its well known pigment-inducing capacity, alpha MSH is able to modulate keratinocyte proliferation and differentiation. Endothelial cell and fibroblast cytokine production and fibroblast collagenase production are also regulated by alpha MSH. The immunosuppressive capacity of alpha MSH is mediated mainly through its effects on monocyte and macrophage functions. Accordingly, alpha MSH downregulates the production of pro-inflammatory cytokines and accessory molecules on antigen-presenting cells. The production of suppressor factors such as IL-10, however, is upregulated by alpha MSH. The in vivo relevance of these data is documented by the finding that systemic application of alpha MSH inhibits the induction and the elicitation of murine contact hyper-sensitivity and induces hapten-specific tolerance. These findings indicate that alpha MSH is part of the mediator network that regulates cutaneous inflammation and hyper-proliferative skin diseases.

Evidence for the differential expression of the functional alpha-melanocyte-stimulating hormone receptor MC-1 on human monocytes

alpha-Melanocyte-stimulating hormone (alpha-MSH) is released by immunocompetent cells as well as the pituitary gland and functions as a potent inhibitor of immune and inflammatory reactions. Therefore, it was investigated whether normal human monocytes express melanocortin (MC) receptors specific for alpha-MSH. Upon FACS analysis using biotin-labeled alpha-MSH, a low number of alpha-MSH binding sites was detectable on unstimulated monocytes. alpha-MSH receptor expression was up-regulated when monocytes were treated with endotoxin (LPS) or mitogen (PHA) for 3 to 5 days and was further augmented by the addition of cytokines such as IL-2, IFN-gamma, IL-4, and IL-10. Adrenocorticotropin, a precursor of alpha-MSH, but not the structurally unrelated beta-MSH, competitively inhibited alpha-MSH binding, suggesting that the receptor expressed on monocytes is specific for alpha-MSH. This was further confirmed by reverse transcription-PCR, which demonstrated that monocytes express mRNA specific for the MC receptor MC-1, which binds alpha-MSH and adrenocorticotropin, whereas mRNA specific for other known melanocortin receptors was not detectable. To investigate whether the immunosuppressing capacity of alpha-MSH is associated with the up-regulation of MC-1, its effect on the expression of costimulatory molecules (CD86 and CD80) on human monocytes was investigated. alpha-MSH significantly inhibited the expression of CD86 on LPS-treated monocytes, which exhibited a high density of MC-1, whereas CD80 expression was not altered. These findings indicate that human monocytes, depending on their activation and maturation state, are able to express MC-1, and up-regulation of MC-1 seems to be required to enable alpha-MSH to modulate immune responses in which costimulatory molecules play a decisive role.

Evidence for the differential expression of the functional alpha-melanocyte-stimulating hormone receptor MC-1 on human monocytes

alpha-Melanocyte-stimulating hormone (alpha-MSH) is released by immunocompetent cells as well as the pituitary gland and functions as a potent inhibitor of immune and inflammatory reactions. Therefore, it was investigated whether normal human monocytes express melanocortin (MC) receptors specific for alpha-MSH. Upon FACS analysis using biotin-labeled alpha-MSH, a low number of alpha-MSH binding sites was detectable on unstimulated monocytes. alpha-MSH receptor expression was up-regulated when monocytes were treated with endotoxin (LPS) or mitogen (PHA) for 3 to 5 days and was further augmented by the addition of cytokines such as IL-2, IFN-gamma, IL-4, and IL-10. Adrenocorticotropin, a precursor of alpha-MSH, but not the structurally unrelated beta-MSH, competitively inhibited alpha-MSH binding, suggesting that the receptor expressed on monocytes is specific for alpha-MSH. This was further confirmed by reverse transcription-PCR, which demonstrated that monocytes express mRNA specific for the MC receptor MC-1, which binds alpha-MSH and adrenocorticotropin, whereas mRNA specific for other known melanocortin receptors was not detectable. To investigate whether the immunosuppressing capacity of alpha-MSH is associated with the up-regulation of MC-1, its effect on the expression of costimulatory molecules (CD86 and CD80) on human monocytes was investigated. alpha-MSH significantly inhibited the expression of CD86 on LPS-treated monocytes, which exhibited a high density of MC-1, whereas CD80 expression was not altered. These findings indicate that human monocytes, depending on their activation and maturation state, are able to express MC-1, and up-regulation of MC-1 seems to be required to enable alpha-MSH to modulate immune responses in which costimulatory molecules play a decisive role.

The murine decorin. Complete cDNA cloning, genomic organization, chromosomal assignment, and expression during organogenesis and tissue differentiation

Decorin, a proteoglycan known to interact with collagen and growth factors, may play key roles during ontogenesis, tissue remodeling, and cancer. We have deciphered the complete protein sequence of the murine decorin by cDNA cloning, elucidated its gene structure and chromosomal location, and investigated its expression in the developing embryo. The decorin protein and the gene were highly conserved vis à vis the human counterpart; however, the murine gene lacked a leader exon, exon Ib, which was found only in the human. Using interspecific backcrossing, we assigned the gene to chromosome 10 just proximally to the Steel gene locus. In situ hybridization studies of developing mouse embryos showed a distinct pattern of expression with a progressive increase of decorin mRNA during ontogenesis. At early stages (day 11 postconception), decorin was detectable only in the floor plate region. Subsequently (days 13-16 postconception), decorin expression was especially prominent in the meninges and mesothelial linings of pericardium, pleura, and coelomic cavity, as well as in the dermis and subepithelial layers of the intestine and urinary bladder. In contrast, the major parenchymal organs were only weakly positive for decorin mRNA. These findings suggest that decorin may play a role in epithelial/mesenchymal interactions during organ development and shaping.

The alpha-operon equivalent genome region in the extreme halophilic archaebacterium Haloarcula (Halobacterium) marismortui

The genome region of the extreme halophilic archaebacterium Haloarcula marismortui equivalent to the alpha-operon of Escherichia coli has been characterized. In H. marismortui, the alpha-operon was found to be located immediately upstream from the S9 gene cluster. The gene order in the halobacterial alpha-operon, given according to the gene products, is tRNA(Ser), HmaS13, HmaS4, HmaS11, and HmaRp alpha. Compared to the corresponding operon from E. coli, the halobacterial gene organization differs in (i) the presence of a gene for tRNA(Ser) (GCU), (ii) the reversed order of the genes for the ribosomal proteins HmaS11 and HmaS4, and (iii) the absence of the gene coding for the ribosomal protein L17. The primary structure of HmaRp alpha shows high similarity to a subunit of eukaryotic RNA polymerase II (YeaRpB3, HsaRpB33), whereas the similarity to the eubacterial alpha-subunit of RNA polymerase is only weak.

Organization and nucleotide sequence of ten ribosomal protein genes from the region equivalent to the spectinomycin operon in the archaebacterium Halobacterium marismortui

The nucleotide sequence has been determined of a 4700 bp region from a ribosomal protein gene cluster of Halobacterium marismortui (Haloarcula marismortui), which is equivalent to part of the spectinomycin operon of Escherichia coli. The genes were localized on the recombinant lambda EMBL3 clone PP*7, which also contains several other ribosomal protein genes from the DNA region in H. marismortui equivalent to the linked S10/spc operon. The genes analysed encode ten ribosomal proteins, namely HmaL5, HmaS14, HmaS8, HmaL6, HL5, HL24, HmaL18, HmaS5, HmaL30 and HmaL15. The gene organization of the archaebacterial cluster is similar to that in eubacteria but has two additional genes, namely those encoding HL5 and HL24, which were identified as extra proteins that are apparently not present in E. coli. These correspond to the gene products of orfd and orfe in Methanococcus vannielii and also have eukaryotic counterparts.

Primary structures of ribosomal proteins from the archaebacterium Halobacterium marismortui and the eubacterium Bacillus stearothermophilus

Approximately 40 ribosomal proteins from each Halobacterium marismortui and Bacillus stearothermophilus have been sequenced either by direct protein sequence analysis or by DNA sequence analysis of the appropriate genes. The comparison of the amino acid sequences from the archaebacterium H marismortui with the available ribosomal proteins from the eubacterial and eukaryotic kingdoms revealed four different groups of proteins: 24 proteins are related to both eubacterial as well as eukaryotic proteins. Eleven proteins are exclusively related to eukaryotic counterparts. For three proteins only eubacterial relatives-and for another three proteins no counterpart-could be found. The similarities of the halobacterial ribosomal proteins are in general somewhat higher to their eukaryotic than to their eubacterial counterparts. The comparison of B stearothermophilus proteins with their E coli homologues showed that the proteins evolved at different rates. Some proteins are highly conserved with 64-76% identity, others are poorly conserved with only 25-34% identical amino acid residues.

Rapid protein purification using phenylbutylamine-Eupergit: a novel method for large-scale procedures

Electrophoretic desorption was used to compare the protein binding capacities of some hydrophobic adsorbents [the phenylbutylamine (PBA) derivatives of Eupergit C and agarose and Phenyl-Sepharose] for low-pressure chromatography. The highest capacity was observed for the bifunctional adsorbent PBA-Eupergit. The hydrophobically adsorbed proteins can be selectively desorbed by decreasing the pH of the eluent due to electrostatic repulsion between positive charges on the adsorbed proteins and positively charged secondary amines on the adsorbent. This was used to purify 1500 U penicillin amidase from E. coli homogenates per gram wet weight of PBA-Eupergit in 50 adsorption-desorption cycles without organic solvents (greater than 90% yield, purification factor = 5.3).