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Biomedical subjects

Michel Bornens

Publications and source records attributed to Michel Bornens.

13 recordsLinked to original sources
PubMed2003

PARP-3 localizes preferentially to the daughter centriole and interferes with the G1/S cell cycle progression.

A novel member of the poly(ADP-ribose) polymerase (PARP) family, hPARP-3, is identified here as a core component of the centrosome. hPARP-3 is preferentially localized to the daughter centriole throughout the cell cycle. The N-terminal domain (54 amino acids) of hPARP-3 is responsible for its centrosomal localization. Full-length hPAPR-3 (540 amino acids, with an apparent mass of 67 kDa) synthesizes ADP-ribose polymers during its automodification. Overexpression of hPARP-3 or its N-terminal domain does not influence centrosomal duplication or amplification but interferes with the G1/S cell cycle progression. PARP-1 also resides for part of the cell cycle in the centrosome and interacts with hPARP-3. The presence of both PARP-1 and PARP-3 at the centrosome may link the DNA damage surveillance network to the mitotic fidelity checkpoint.

3T3 Cells↗
PubMed2003

Fission yeast cdc31p is a component of the half-bridge and controls SPB duplication.

The fission yeast spindle pole body (SPB) is a nucleus-associated organelle that duplicates once each cell cycle during interphase. Duplicated SPBs serve as the poles of an intranuclear mitotic spindle after their insertion into the nuclear envelope in mitosis (Ding et al., Mol. Biol. Cell 8, 1461-1479). Here, we report the identification and characterization of Schizosaccharomyces pombe cdc31p, a member of the conserved calcium-binding centrin/CDC31 family. Immunofluorescence and immunoelectron microscopy show that cdc31p is a SPB component localized at the half-bridge structure of the SPB. cdc31 is an essential gene and Deltacdc31 cells and cdc31 conditional mutant cells arrest in mitosis with a monopolar mitotic spindle organized from a single SPB. EM analysis demonstrates that mutant cdc31 cells fail to duplicate the SPB. In addition, cdc31p exhibits genetic interactions with the SPB component sad1p and is required for sad1p localization. Finally, cdc31 mutant can undergo single or multiple rounds of septation before the exit from mitosis, suggesting that cdc31p activity or SPB duplication may be required for the proper coordination between the exit from mitosis and the initiation of septation.

Amino Acid Sequence↗
PubMed2003

Dissociating the centrosomal matrix protein AKAP450 from centrioles impairs centriole duplication and cell cycle progression.

Centrosomes provide docking sites for regulatory molecules involved in the control of the cell division cycle. The centrosomal matrix contains several proteins, which anchor kinases and phosphatases. The large A-Kinase Anchoring Protein AKAP450 is acting as a scaffolding protein for other components of the cell signaling machinery. We selectively perturbed the centrosome by modifying the cellular localization of AKAP450. We report that the expression in HeLa cells of the C terminus of AKAP450, which contains the centrosome-targeting domain of AKAP450 but not its coiled-coil domains or binding sites for signaling molecules, leads to the displacement of the endogenous centrosomal AKAP450 without removing centriolar or pericentrosomal components such as centrin, gamma-tubulin, or pericentrin. The centrosomal protein kinase A type II alpha was delocalized. We further show that this expression impairs cytokinesis and increases ploidy in HeLa cells, whereas it arrests diploid RPE1 fibroblasts in G1, thus further establishing a role of the centrosome in the regulation of the cell division cycle. Moreover, centriole duplication is interrupted. Our data show that the association between centrioles and the centrosomal matrix protein AKAP450 is critical for the integrity of the centrosome and for its reproduction.

A Kinase Anchor Proteins↗
PubMed2003

Centrin4p, a novel mammalian centrin specifically expressed in ciliated cells.

Centriole assembly plays an important role in centrosome duplication during the cell cycle and is a prerequisite for cilia formation during the differentiation of ciliated cells. In spite of numerous investigations, the molecular machinery that governs centriole/basal body formation remains enigmatic. Recent reports suggest that the ubiquitously expressed mammalian centrins, centrin2p and centrin3p, could be involved in the centriole duplication process. To better understand the specific functions of these proteins, we performed a systematic search for novel mammalian centrins. We isolated a cDNA and the corresponding gene coding for a novel murine centrin, centrin4p, which is more closely related to centrin2p. Like centrin2p, centrin4p accumulates to centrioles and procentrioles when ectopically expressed in HeLa cells. However, centrin4p possesses two splice variants that do not localize to centrioles, suggesting a posttranscriptional regulation mechanism. We also observed that centrin4p does not share the same centriolar targeting properties with centrin2p and 3p, indicating that these proteins could recognize different centriolar partners. Centrin4 mRNA possesses a restricted expression profile and is only detected in brain, kidney, lung, and ovary. In brain, centrin4p is exclusively expressed in ependymal and choroidal ciliated cells where it is localized to basal bodies. Together, our present data suggest that centrin4p could be more specifically involved in basal bodies assembly or in a subsequent step of ciliogenesis.

Amino Acid Sequence↗
PubMed2003

The Golgi apparatus at the cell centre.

In non-polarised mammalian cells, the Golgi apparatus is localised around the centrosome and actively maintained there. Microtubules and molecular motor activity are required for determining both the localisation and organisation of the Golgi apparatus. Other factors, however, also appear necessary for regulating both the static steady-state distribution of this organelle and its relationship with microtubule minus-end-anchoring activities of the centrosome. Several non-motor microtubule-binding proteins have now been found to be associated with the Golgi apparatus. Recent advances suggest that, in addition to important roles in cell motility, polarisation and differentiation, the interplay between Golgi apparatus and centrosome could participate in other physiological processes such as intracellular signalling, mitosis and apoptosis.

Animals↗
PubMed2003

Kar9 asymmetrical loading on spindle poles mediates proper spindle alignment in budding yeast.

In the February 21 issue of Cell, demonstrate that asymmetrical loading of Kar9 onto astral microtubules (MTs) emanating from the bud-ward-directed spindle pole ensures delivery of this spindle pole to the bud. Kar9 mediates alignment of the spindle with the cell polarity axis through a Myo2-dependent mechanism that reorients astral MTs toward the bud.

CDC28 Protein Kinase, S cerevisiae↗
PubMed2002

Microtubule release from the centrosome in migrating cells.

In migrating cells, force production relies essentially on a polarized actomyosin system, whereas the spatial regulation of actomyosin contraction and substrate contact turnover involves a complex cooperation between the microtubule (MT) and the actin filament networks (Goode, B.L., D.G. Drubin, and G. Barnes. 2000. Curr. Opin. Cell Biol., 12:63-71). Targeting and capture of MT plus ends at the cell periphery has been described, but whether or not the minus ends of these MTs are anchored at the centrosome is not known. Here, we show that release of short MTs from the centrosome is frequent in migrating cells and that their transport toward the cell periphery is blocked when dynein activity is impaired. We further show that MT release, but not MT nucleation or polymerization dynamics, is abolished by overexpression of the centrosomal MT-anchoring protein ninein. In addition, a dramatic inhibition of cell migration was observed; but, contrary to cells treated by drugs inhibiting MT dynamics, polarized membrane ruffling activity was not affected in ninein overexpressing cells. We thus propose that the balance between MT minus-end capture and release from the centrosome is critical for efficient cell migration.

Animals↗
PubMed2002

The Rho-associated protein kinase p160ROCK is required for centrosome positioning.

The p160-Rho-associated coiled-coil-containing protein kinase (ROCK) is identified as a new centrosomal component. Using immunofluorescence with a variety of p160ROCK antibodies, immuno EM, and depletion with RNA interference, p160ROCK is principally bound to the mother centriole (MC) and an intercentriolar linker. Inhibition of p160ROCK provoked centrosome splitting in G1 with the MC, which is normally positioned at the cell center and shows little motion during G1, displaying wide excursions around the cell periphery, similar to its migration toward the midbody during cytokinesis. p160ROCK inhibition late after anaphase in mitosis triggered MC migration to the midbody followed by completion of cell division. Thus, p160ROCK is required for centrosome positioning and centrosome-dependent exit from mitosis.

Anaphase↗
PubMed2002

Centrosome inheritance: birthright or the privilege of maturity?

Budding yeast cells exhibit a defined mode of centrosome inheritance--the 'old' spindle pole body always segregates into the bud. But it is the astral microtubule-cortex interaction which matters for controlling the asymmetric localization of Bfa1p/Bub2 at spindle pole bodies.

Animals↗
PubMed2002

Centrosome composition and microtubule anchoring mechanisms.

Centrosomes of animal cells and spindle pole bodies of fungi are the major microtubule nucleating centers. Recent studies indicate that their capacity to organize microtubule arrays rests on elaborate control of the anchoring and release of the nucleated microtubules. Although common molecular mechanisms are likely to be involved in both cases, the centrosome from animal cells shows considerable complexity and flexibility, which contrasts with the simple laminar organization of spindle pole bodies in fungi. The role of the centriole pair in controlling both the structural stability and the activity of the centrosome in animal cells is now becoming clearer. The potential use of the generational asymmetry of centrosomes or spindle pole bodies for controlling cell polarity is also a growing theme.

Animals↗
PubMed2002

The overexpression of GMAP-210 blocks anterograde and retrograde transport between the ER and the Golgi apparatus.

Golgi Microtubule-Associated Protein (GMAP)-210 is a peripheral coiled-coil protein associated with the cis-Golgi network that interacts with microtubule minus ends. GMAP-210 overexpression has previously been shown to perturb the microtubule network and to induce a dramatic enlargement and fragmentation of the Golgi apparatus (Infante C, Ramos-Morales F, Fedriani C, Bornens M, Rios RM. J Cell Biol 1999; 145: 83-98). We now report that overexpressing GMAP-210 blocks the anterograde transport of both a soluble form of alkaline phosphatase and the hemagglutinin protein of influenza virus, an integral membrane protein, between the endoplasmic reticulum and the cis/medial (mannosidase II-positive) Golgi compartment. Retrograde transport of the Shiga toxin B-subunit is also blocked between the Golgi apparatus and the endoplasmic reticulum. As a consequence, the B-subunit accumulates in compartments positive for GMAP-210. Ultrastructural analysis revealed that, under these conditions, the Golgi complex is totally disassembled and Golgi proteins as well as proteins of the intermediate compartment are found in vesicle clusters distributed throughout the cell. The role of GMAP-210 on membrane processes at the interface between the endoplasmic reticulum and the Golgi apparatus is discussed in the light of the property of this protein to bind CGN membranes and microtubules.

Alkaline Phosphatase↗