Biomedical subjects

V Doye

Publications and source records attributed to V Doye.

25 records · Page 2Linked to original sources

PubMed1992

A new subclass of nucleoporins that functionally interact with nuclear pore protein NSP1.

NSP1 is a nuclear pore protein (nucleoporin) essential for cell growth. To identify the components that functionally interact with NSP1 in the living cell, we developed a genetic screen for mutants that are lethal in a genetic background of mutated, but not wild type NSP1. Fourteen synthetic lethal mutants were obtained, belonging to at least four different complementation groups. The genes of two complementation groups, NSP116 and NSP49, were cloned. Like the previously described nucleoporins, these genes encode proteins with many repeat sequences. NSP116 and NSP49, however, contain a new repetitive sequence motif 'GLFG', which classifies them as a subclass of nucleoporins. NSP116 and NSP49, tagged with the IgG binding domain of protein A and expressed in yeast, are located at the nuclear envelope. These data provide in vivo evidence that distinct subclasses of nucleoporins physically interact or share overlapping function in nuclear pore complexes.

Amino Acid Sequence↗

PubMed1992

High expression of stathmin in multipotential teratocarcinoma and normal embryonic cells versus their early differentiated derivatives.

Stathmin is a ubiquitous cytoplasmic protein, phosphorylated in response to agents regulating the proliferation, the differentiation and the specialized functions of cells, in a way possibly integrating the actions of diverse concomitant regulatory signals. Its expression is also regulated in relation with cell proliferation and differentiation and reaches a peak at the neonatal stage. To assess the possible role of stathmin at earlier stages of development, we examined its expression and regulation in embryonal carcinoma (EC) and derived cell lines as well as in the early mouse embryo. Interestingly, stathmin is highly abundant in the undifferentiated, multipotential cells of the F9, 1003 and 1009 EC cell lines. Its high expression markedly decreased, both at the protein and mRNA levels, when F9 cells were induced to differentiate into endodermal-like cells with retinoic acid and dibutyryl-cAMP. Stathmin was also much less abundant in differentiated cell lines such as the trophectodermal line TDM-1, as well as in several F9- and 1003-derived cell lines committed to differentiate towards the mesodermal and neuroectodermal lineages but still proliferating. Therefore, the observed decrease of stathmin expression is not related to the reduced proliferation rate but rather to the differentiation of the multipotential EC cells. The immunocytochemical pattern of stathmin expression during early mouse development indicated that stathmin is also highly abundant in the multipotential cells of the inner cell mass of the blastula, whereas it is much lower in the differentiated trophectodermal cells. These results confirm the physiological relevance of the observations with EC cells, and suggest that stathmin, in addition to its high expression at later stages of development and in the adult nervous system, may be considered as a new marker of the multipotential cells of the early mouse embryo.

Animals↗

PubMed1990

Phosphorylation of stathmin and other proteins related to nerve growth factor-induced regulation of PC12 cells.

We previously identified a set of soluble proteins whose phosphorylation could be originally related to the multihormonal regulations of anterior pituitary cells. Among these proteins, stathmin (proteins 7 and 8) was found to be ubiquitous and mostly abundant in neurons. Interestingly, stathmin and some other phosphoproteins of the same set could be identified also in PC12 cells in culture. Their phosphorylation was stimulated in these cells by nerve growth factor (NGF) in a way associated with its short term actions, probably corresponding to the early steps of its neuronal differentiating activity. In addition, the same proteins had their phosphorylation stimulated in the presence of fibroblast growth factor, known to stimulate PC12 cell differentiation in a way similar to NGF. A pharmacological analysis allowed us to distinguish three characteristic subsets of phosphoproteins, respectively, affected by cAMP-dependent agents, by cAMP-independent ones, or by both types of agents. Moreover, phosphorylation of stathmin and some other proteins was additive in the presence of NGF and of the cAMP-promoting agent forskolin. Altogether, the present results unravel some intracellular mechanisms related to the regulation of PC12 cells by extracellular effectors. They extend to the regulation of cell differentiation in our recent model for stathmin (Sobel, A., Boutterin, M-C., Beretta, L., Chneiweiss, H., Doye, V., and Peyro-Saint-Paul, H. (1989) J. Biol. Chem. 264, 3765-3772) as an ubiquitous intracellular relay possibly integrating the actions of diverse second messenger pathways involved in cell regulations.

Adenosine↗

PubMed1990

A single amino acid difference distinguishes the human and the rat sequences of stathmin, a ubiquitous intracellular phosphoprotein associated with cell regulations.

Stathmin is a ubiquitous phosphoprotein proposed to play a general role as an intracellular relay integrating diverse regulatory signals of the cell's environment. We used a rat stathmin probe to isolate two classes of cDNAs coding for the human protein and corresponding to the usage of different polyadenylation sites. Compared to the rat sequences, they displayed a very high conservation both at the nucleic acid and the deduced protein sequence levels, with a single conservative amino acid difference. Further analysis of the protein sequence revealed novel putative phosphorylation sites, as well as internal repeated sequences which might reflect structural features involved in the molecular mechanisms by which stathmin fulfills its biological functions. The extreme conservation of the entire stathmin sequence further stresses the essential and general role of stathmin in cell regulations.

Amino Acid Sequence↗

PubMed1990

Developmental tissue expression and phylogenetic conservation of stathmin, a phosphoprotein associated with cell regulations.

Stathmin is a 19-kDa phosphoprotein presumably involved in regulations of cell proliferation, differentiation, and functions as an intracellular relay for extracellular signals activating diverse second messenger pathways. Antisera prepared against the whole protein or against two peptides (residues 15-27 and 134-149) recognized the two isoforms (alpha and beta) of stathmin in their different phosphorylated states on immunoblots. Also, the possible existence of a family of stathmin-related proteins is suggested by the detection with some sera of proteins of 17, 21, and 60 kDa in brain. Stathmin and its diverse molecular forms were detected in all mouse tissues tested, in varying concentrations. Depending on the tissue, it is 2-100 times more abundant in the neonate than in the adult. It is most abundant in brain at both developmental stages, the protein levels being paralleled by the expression of the corresponding mRNA as detected with a specific cDNA probe. Antibodies directed against the rat protein also reacted with stathmin-like proteins in the brain of other mammals, birds, reptiles, amphibians, and some fish species, and the various isoforms could be recognized on immunoblots. In conclusion, our results suggest that stathmin is most likely involved in two distinct types of regulations: 1) "developmental" regulations, related to cell proliferation, differentiation, and maturation, and 2) "functional" regulations mostly at the adult stage, and typically in the nervous system. In addition, stathmin is also phylogenetically well conserved at least in vertebrates. Together, these observations support the proposed ubiquitous nature and general importance of stathmin in biological regulations.

Aging↗

PubMed1989

A single cDNA encodes two isoforms of stathmin, a developmentally regulated neuron-enriched phosphoprotein.

Stathmin, a 19-kDa neuron-enriched soluble phosphoprotein, has been recently proposed as an ubiquitous intracellular relay for the diverse extracellular signals regulating cell proliferation, differentiation, and functions through various second messenger pathways (Sobel, A., Boutterin, M.C., Beretta, L., Chneiweiss, H., Doye, V., and peyro-Saint-Paul, H. (1989) J. Biol. Chem. 264, 3765-3772). Internal sequences of the protein from rat brain were determined after purification by two-dimensional polyacrylamide gel electrophoresis, electrotransfer onto Immobilon, and in situ proteolysis. Oligonucleotide mixtures based on these sequences were used to clone a cDNA for stathmin from a rat PC12 cell lambda gt 10 library. The deduced amino acid sequence reveals partial homologies with the coiled coil structural regions of several intracellular matrix phosphoproteins. Using this cDNA as a probe, we show that the expression of stathmin mRNA parallels that of the protein during brain ontogenesis, reaching a maximum at the neonatal stage. In vitro translation of the derived cRNA yielded all the known molecular forms of stathmin, namely its alpha and beta isoforms in their unphosphorylated and phosphorylated states. Thus, a single cDNA codes for both biologically relevant isoforms of the protein, indicating that they differ by co- or post-translational modifications.

Adrenal Gland Neoplasms↗

PubMed1989

Intracellular substrates for extracellular signaling. Characterization of a ubiquitous, neuron-enriched phosphoprotein (stathmin).

We previously identified (Sobel, A., and Tashjian, A. H., Jr. (1983) J. Biol. Chem. 258, 10312-10324) a group of cytoplasmic proteins whose phosphorylation could be related to the regulation by extracellular effectors of cells as different as pituitary and muscle cells. Among these phosphoproteins, proteins "7" and "8" (Mr approximately 19,000, pI approximately 5.8-6.0), that we now designate P1 and P2, are very abundant in rat brain. Partial purification of these proteins was therefore achieved after 100 degrees C precipitation of a rat brain-soluble fraction and further fractionation of the supernatant by ion exchange chromatography. Several related non-phosphorylated (N1, N2) and phosphorylated (P3) proteins were also identified in the heat-resistant supernatant. Antisera raised against P2 extracted from nitrocellulose blots of semipreparative two-dimensional gels recognized all the proteins N1, N2, P1, P2, and P3, confirming that they belong to the same protein family, and suggesting that they are likely various forms of a single protein core. The same protein could be detected biochemically and immunologically at various concentrations in all the tissues or cell types from diverse mammalian and nonmammalian species tested. Together with our previous data relating its phosphorylation to the regulation of the proliferation, differentiation, and/or the functions of the cells considered, this observation leads us to suggest that it might be an ubiquitous regulatory phosphoprotein playing the role of an intracellular "relay" for extracellular signals, after their binding to specific membrane receptors and the generation of second messengers. We propose to name this protein stathmin, from the greek "stathmos" (relay).

Animals↗