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Accueil > Agenda > Les séminaires Jean Roche > Les récepteurs purinergiques, de nouveaux modulateurs de la migration des (...)

Les récepteurs purinergiques, de nouveaux modulateurs de (...)

Lundi 5 décembre 2005, salle Lissitzky.


1 : Mol Cell Neurosci. 2005 Nov ;30(3):418-28. Epub 2005 Sep 15.

Evidences that beta1 integrin and Rac1 are involved in the overriding effect of laminin on myelin-associated glycoprotein inhibitory activity on neuronal cells.

Laforest S, Milanini J, Parat F, Thimonier J, Lehmann M.

FRE CNRS 2737, Faculte de Pharmacie, 27 Bd Jean Moulin, 13005 Marseille, France.

During neurite elongation, migrating growth cones encounter both permissive and inhibitory substrates, such as laminin and MAG (myelin-associated glycoprotein), respectively. Here, we demonstrated on two neuronal cell lines (PC12 and N1E-115), that laminin and collagen hampered, in a dose-dependent manner, MAG inhibitory activity on several integrin functions, i.e., neurite growth, cell adhesion and cell spreading. Using a function blocking antibody, in PC12 cells, we showed that alpha1beta1 integrin is required in these phenomena. In parallel, we observed that MAG perturbs actin dynamics and lamellipodia formation during early steps of cell spreading. This seemed to be independent of RhoA activation, but dependent of Rac-1 inhibition by MAG. Laminin overrode MAG activity on actin and prevented MAG inhibition NGF-induced Rac1 activation. In conclusion, we evidenced antagonistic signaling between MAG receptors and beta1 integrins, in which Rac-1 may have a central function.

2 : Cancer Res. 2005 Mar 15 ;65(6):2433-40.

Antiangiogenic concentrations of paclitaxel induce an increase in microtubule dynamics in endothelial cells but not in cancer cells.

Pasquier E, Honore S, Pourroy B, Jordan MA, Lehmann M, Briand C, Braguer D.

Interactions Entre Systemes Proteiques Et Differenciation Dans La Cellule Tumorale, FRE-Centre National de la Recherche Scientifique, Universite de la Mediterranee, Marseille, France.

Microtubule-targeted drugs such as paclitaxel exhibit potent antiangiogenic activity at very low concentrations, but the mechanism underlying such an effect remains unknown. To understand the involvement of microtubules in angiogenesis, we analyzed the dynamic instability behavior of microtubules in living endothelial cells [human microvascular endothelial cells (HMEC-1) and human umbilical vascular endothelial cells (HUVEC)] following 4 hours of paclitaxel treatment. Unexpectedly, antiangiogenic concentrations of paclitaxel (0.1-5 nmol/L) strongly increased microtubule overall dynamicity in both HMEC-1 (86-193%) and HUVEC (54-83%). This increase was associated with increased microtubule growth and shortening rates and extents and decreased mean duration of pauses. The enhancement of microtubule dynamics by paclitaxel seemed to be specific to antiangiogenic concentrations and to endothelial cells. Indeed, cytotoxic concentration (100 nmol/L) of paclitaxel suppressed microtubule dynamics by 40% and 54% in HMEC-1 and HUVECs, respectively, as observed for all tested concentrations in A549 tumor cells. After 4 hours of drug incubation, antiangiogenic concentrations of paclitaxel that inhibited endothelial cell proliferation without apoptosis (1-5 nmol/L) induced a slight decrease in anaphase/metaphase ratio, which was more pronounced and associated with increased mitotic index after 24 hours of incubation. Interestingly, the in vitro antiangiogenic effect also occurred at 0.1 nmol/L paclitaxel, a concentration that did not alter mitotic progression and endothelial cell proliferation but was sufficient to increase interphase microtubule dynamics. Altogether, our results show that paclitaxel mediates antiangiogenesis by an increase in microtubule dynamics in living endothelial cells and suggest that the impairment of interphase microtubule functions is responsible for the inhibition of angiogenesis.

3 : International journal of cancer 91 (3) : 300-308 FEB 1 2001

Regulation of urokinase plasminogen activator/plasmin-mediated invasion of melanoma cells by the integrin vitronectin receptor alpha(v)beta(3)

Khatib AM, Nip J, Fallavollita L, Lehmann M, Jensen G, Brodt P

The integrin vitronectin receptor alpha (v)beta (3) is a mediator of cellular migration and invasion and has been identified as a marker of progression in malignant melanoma. Using a human melanoma model, we have previously shown that this receptor was coordinately expressed with the receptor for the urokinase plasminogen activator (uPAR). In our present study, the link between these receptors was further investigated by assessing the effect of alpha (v)beta (3) ligation on uPAR transcription and function. Using the reverse transcription-polymerase chain reaction, we found that receptor ligation by immobilized monoclonal antibodies (MAbs) induced a rapid increase (up to 4.5 fold) in uPAR mRNA levels, which was maximal 4 hr after cell attachment. An increase was also noted in plasminogen activator inhibitor type-1 (PAI-1) mRNA levels (2.7-fold), but none was noted in uPA levels. In addition, ligation of alpha (v)beta (3) resulted in a significant increase in cell surface-associated plasmin revels, which coincided with a 2- to 3-fold increase in cell invasion as measured in the Matrigel invasion assay. This increase in invasion could in turn be abolished by antibodies directed to UPA and uPAR and by the plasmin inhibitors epsilon -aminocaproic acid and aprotinin, Furthermore, ligation of the integrin alpha (v)beta (3) triggered a rapid increase of up to 12-fold in total cellular PKC activity, and this coincided with the redistribution of PKC beta, but not PKC alpha, from the cytosol to the membrane. Treatment of the cells with the PKC beta -specific inhibitor LY379196 blocked uPAR and PAI-1 mRNA induction and reduced the increase in cell invasion due to alpha (v)beta (3) ligation, confirming the involvement of this isoform in the response. The results provide evidence that the vitronectin receptor can enhance invasion by regulating the uPAR/uPA/plasmin system of proteolysis and implicate PKC beta as an intermediate in the activation pathway. (C) 2001 Wiley-Liss, Inc.

Addresses : Brodt P (reprint author), Royal Victoria Hosp, Room H6-25,687 Pine Ave W, Montreal, PQ H3A 1A1 Canada Royal Victoria Hosp, Montreal, PQ H3A 1A1 Canada Fac Pharm, Marseille, France McGill Univ, Dept Surg, Montreal, PQ H3A 2T5 Canada McGill Univ, Dept Med, Montreal, PQ H3A 2T5 Canada

4 : Eur J Biochem. 1999 May ;261(3):659-66.

Biogenesis of alpha6beta4 integrin in a human colonic adenocarcinoma cell line involvement of calnexin.

Rigot V, Andre F, Lehmann M, Lissitzky JC, Marvaldi J, Luis J.

Laboratoire de Biochimie Cellulaire, CNRS UPRESA 6032, Faculte de Pharmacie, Marseille, France.

The heterodimer alpha6beta4 is a major integrin and the main laminin receptor in epithelia. The alpha6 integrin subunit is proteolytically cleaved, probably by furin, and glycosylated during its biosynthesis. In the present work, we have investigated the kinetics of the assembly process of alpha6beta4 heterodimers in the colonic adenocarcinoma cell line HT29-D4. We demonstrate that the association of alpha6 and beta4 precursors occurs within the ER, while the endoproteolytic cleavage of pro-alpha6 occurs later, probably in the trans-Golgi network. When pro-alpha6 was blocked within the ER by treatment with brefeldin A, its maturation processing was completely prevented without any consequence on its association with beta4 subunit. Low temperature (20 degrees C) also blocked pro-alpha6 maturation, like brefeldin A, but in addition impaired the integrin assembly. Calnexin, an ER resident protein chaperone, was found to be associated with both the alpha6 and beta4 subunit precursors. Our data suggest that calnexin might be responsible for the prolonged retention of pro-alpha6 within the ER compartment and for the defect of integrin subunit association observed at low temperature.

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