Mapping of the Physcomitrella patens proteome

The moss Physcomitrella patens is unique among land plants due to the high rate of homologous recombination in its nuclear DNA. The feasibility of gene targeting makes Physcomitrella an unrivalled model organism in the field of plant functional genomics. To further extend the potentialities of this seed-less plant we aimed at exploring the P. patens proteome. Experimental conditions had to be adopted to meet the special requirements connected to the investigations of this moss. Here we describe the identification of 306 proteins from the protonema of Physcomitrella. Proteins were separated by two dimensional electrophoresis, excised form the gel and analysed by means of mass spectrometry. This reference map will lay the basis for further profound studies in the field of Physcomitrella proteomics.     

Melanoma Cells Treated with GGTI and IFN-γ Allow Murine Vaccination and Enhance Cytotoxic Response against Human Melanoma Cells

Background

Suboptimal activation of T lymphocytes by melanoma cells is often due to the defective expression of class I major histocompatibility antigens (MHC-I) and costimulatory molecules. We have previously shown that geranylgeranyl transferase inhibition (done with GGTI-298) stimulates anti-melanoma immune response through MHC-I and costimulatory molecule expression in the B16F10 murine model [1].

Methodology/Principal Findings

In this study, it is shown that vaccination with mIFN-gand GGTI-298 pretreated B16F10 cells induces a protection against untreated tumor growth and pulmonary metastases implantation. Furthermore, using a human melanoma model (LB1319-MEL), we demonstrated that in vitro treatment with hIFN-γ and GGTI-298 led to the up regulation of MHC-I and a costimulatory molecule CD86 and down regulation of an inhibitory molecule PD-1L. Co-culture experiments with peripheral blood mononuclear cells (PBMC) revealed that modifications induced by hIFN-γ and GGTI-298 on the selected melanoma cells, enables the stimulation of lymphocytes from HLA compatible healthy donors. Indeed, as compared with untreated melanoma cells, pretreatment with hIFN-γ and GGTI-298 together rendered the melanoma cells more efficient at inducing the: i) activation of CD8 T lymphocytes (CD8+/CD69+); ii) proliferation of tumor-specific CD8 T cells (MelanA-MART1/TCR+); iii) secretion of hIFN-γ; and iv) anti-melanoma specific cytotoxic cells.

Conclusions/Significance

These data indicate that pharmacological treatment of melanoma cell lines with IFN-γ and GGTI-298 stimulates their immunogenicity and could be a novel approach to produce tumor cells suitable for vaccination and for stimulation of anti-melanoma effector cells.     

Production of highly 13C-labeled polyphenols in Vitis vinifera cell bioreactor cultures

The use of Vitis vinifera cells grown in a 2 l-stirred tank bioreactor for producing isotopically 13C-labeled phenolic substances is presented. Several culture parameters were optimized to achieve characteristics of growth and polyphenol metabolism similar to that recorded in shake flasks. Administration of [1-13C]L-phenylalanine (3 mM) to grape cell suspension cultures led to the production of 13C-labeled stilbenes (trans- and cis-piceids), catechins (catechin and epicatechin) and anthocyanins (delphinidin-, cyanidin-, petunidin-, peonidin- and malvidin-3-O-beta-glucosides). Incorporation of [1-13C]L-phenylalanine into polyphenols was measured by means of 13C satellites in the proton NMR spectrum and EA-IRMS. The enrichment of labeling obtained for all the compounds (between 40 and 65%) is sufficient to investigate their absorption and metabolism in humans.     

Importin alpha associates with membranes and participates in nuclear envelope assembly in vitro

Importin alpha is well known as an adaptor that functions with Importin beta in the nuclear import of proteins containing specific nuclear localization signals (NLSs). We show here that either an excess or a lack of Importin alpha blocks nuclear envelope (NE) assembly in vitro, and our data suggest that soluble Importin alpha functions in NE assembly in conjunction with NLS-containing partner proteins. Surprisingly, a significant proportion of Importin alpha is found to fractionate with Xenopus egg membranes. We demonstrate that membrane association of Importin alpha is regulated by phosphorylation. Using mutant forms of Importin alpha that either do not bind membranes or are not released from them by phosphorylation, we provide evidence that membrane-associated Importin alpha is required for NE formation. Unlike other functions of Importin alpha, this membrane-associated activity does not require interaction with NLS proteins.     

Rh-RhAG/ankyrin-R,a new interaction site between the membrane bilayer and the red cell skeleton,is impaired by Rh(null)-associated mutation

Several studies suggest that the Rh complex represents a major interaction site between the membrane lipid bilayer and the red cell skeleton, but little is known about the molecular basis of this interaction. We report here that ankyrin-R is capable of interacting directly with the C-terminal cytoplasmic domain of Rh and RhAG polypeptides. We first show that the primary defect of ankyrin-R in normoblastosis (nb/nb) spherocytosis mutant mice is associated with a sharp reduction of RhAG and Rh polypeptides. Secondly, our flow cytometric analysis of the Triton X-100 extractability of recombinant fusion proteins expressed in erythroleukemic cell lines suggests that the C-terminal cytoplasmic domains of Rh and RhAG are sufficient to mediate interaction with the erythroid membrane skeleton. Using the yeast two-hybrid system, we demonstrate a direct interaction between the cytoplasmic tails of Rh and RhAG and the second repeat domain (D2) of ankyrin-R. This finding is supported by the demonstration that the substitution of Asp-399 in the cytoplasmic tail of RhAG, a mutation associated with the deficiency of the Rh complex in one Rhnull patient, totally impaired interaction with domain D2 of ankyrin-R. These results identify the Rh/RhAG-ankyrin complex as a new interaction site between the red cell membrane and the spectrin-based skeleton, the disruption of which might result in the stomato-spherocytosis typical of Rhnull red cells.     

Intracellular maturation and transport of tumor necrosis factor alpha converting enzyme

The tumor necrosis factor alpha converting enzyme (TACE) activity is required for the shedding of a variety of biologically active membrane bound precursors. The activation of TACE necessitates the proteolytic cleavage of its prodomain, a process that was suggested to be catalyzed by the proprotein convertase furin. However, the involvement of furin in this activation process has never been experimentally demonstrated. We have shown that the furinlike cleavage site (R-V-K-R(214)) localized between the prodomain and the metalloprotease domain of TACE is the sole site that can be in vitro cleaved by furin. In Cos7 cells, the release of TACE-processed substrates was reduced by the overexpression of the furin-specific proprotein convertase inhibitor Portland alpha1-antitrypsin inhibitor, but the release of TACE-processed substrates was increased by overexpression of furin in LoVo cells (deficient in furin activity) in which a mature form of TACE was identified. The immature form of TACE was detected at the surface of LoVo cells and at the surface of Cos7 and HT29 cells upon proprotein convertase inhibition. These results suggest that furin is the major proprotein convertase involved in the maturation/activation of TACE which is not a prerequisite for its cell-surface expression.