Publications
ARTICLES
You will find below my articles
Antkowiak A, Viaud J, Severin S, Zanoun M, Ceccato L, Chicanne G, Strassel C, Eckly A, Leon C, Gachet C, Payrastre B, Gaits-Iacovoni F. J Thromb Haemost. 2016 Jun;14(6):1268-84
Essentials Information about the formation of the demarcation membrane system (DMS) is still lacking. We investigated the role of the cytoskeleton in DMS structuration in megakaryocytes. Cdc42/Pak-dependent F-actin remodeling regulates DMS organization for proper megakaryopoiesis. These data highlight the mandatory role of F-actin in platelet biogenesis.
Dütting S, Gaits-Iacovoni F, Stegner D, Popp M, Antkowiak A, van Eeuwijk JMM, Nurden P, Stritt S, Heib T, Aurbach K, Angay O, Cherpokova D, Heinz N, Baig AA, Gorelashvili MG, Gerner F, Heinze KG, Ware J, Krohne G, Ruggeri ZM, Nurden AT, Schulze H, Modlich U, Pleines I, Brakebusch C, Nieswandt B. Nat Commun. 2017 Jun 15;8:15838
Blood platelets are produced by large bone marrow (BM) precursor cells, megakaryocytes (MKs), which extend cytoplasmic protrusions (proplatelets) into BM sinusoids. Main results position Cdc42 (go-signal) and RhoA (stop-signal) at the centre of a molecular checkpoint downstream of GPIb that controls transendothelial platelet biogenesis. Our results may open new avenues for the treatment of platelet production disorders and help to explain the thrombocytopenia in patients with Bernard-Soulier syndrome, a bleeding disorder caused by defects in GPIb-IX-V.
Antkowiak A, Guillotin A, Boiero Sanders M, Colombo J, Vincentelli R, Michelot A. PLoS Biol. 2019 Jun 10;17(6):e3000317
Within the cytoplasm of a single cell, several actin networks can coexist with distinct sizes, geometries, and protein compositions. These actin networks assemble in competition for a limited pool of proteins present in a common cellular environment. To predict how two distinct networks of actin filaments control this balance, the simultaneous assembly of Arp2/3-branched networks and formin-linear networks of actin filaments around polystyrene microbeads was investigated with a range of actin accessory proteins. This work supports a general model in which the size of distinct actin networks is determined by their relative capacity to assemble in a common and competing environment.
Colombo J*, Antkowiak A*, Kogan K, Kotila T, Elliott J, Guillotin A, Lappalainen P, Michelot A. (* co first authors) Nat Commun 12, 548 (2021).
Actin polymerization provides force for vital processes of the eukaryotic cell, but our understanding of actin dynamics and energetics remains limited due to the lack of high-quality probes. Most current probes affect dynamics of actin or its interactions with actin-binding proteins (ABPs), and cannot track the bound nucleotide. Here, we identify a family of highly sensitive fluorescent nucleotide analogues structurally compatible with actin. We demonstrate that these fluorescent nucleotides bind to actin, maintain functional interactions with a number of essential ABPs, are hydrolyzed within actin filaments, and provide energy to power actin-based processes. These probes also enable monitoring actin assembly and nucleotide exchange with single-molecule microscopy and fluorescence anisotropy kinetics, therefore providing robust and highly versatile tools to study actin dynamics and functions of ABPs.
Boiero Sanders M, Toret CP, Guillotin A, Antkowiak A, Vannier T, Robinson RC, Michelot A. EMBO J. Feb 18;e107982 (2022)
A paradox of eukaryotic cells is that while some species assemble a complex actin cytoskeleton from a single ortholog, other species utilize a greater diversity of actin isoforms. The physiological consequences of using different actin isoforms, and the molecular mechanisms by which highly conserved actin isoforms are segregated into distinct networks, are poorly known. Here, we sought to understand how a simple biological system, composed of a unique actin and a limited set of actin-binding proteins, reacts to a switch to heterologous actin expression. Using yeast as a model system and biomimetic assays, we show that such perturbation causes drastic reorganization of the actin cytoskeleton. Our results indicate that defective interaction of a heterologous actin for important regulators of actin assembly limits certain actin assembly pathways while reinforcing others. Expression of two heterologous actin variants, each specialized in assembling a different network, rescues cytoskeletal organization and confers resistance to external perturbation. Hence, while species using a unique actin have homeostatic actin networks, actin assembly pathways in species using several actin isoforms may act more independently.
Oprescu A, Michel D, Antkowiak A, Vega E, Viaud J, Courtneidge SA, Eckly A, de la Salle H, Chicanne G, Payrastre B, Gaits-Iacovoni F. Sci Rep 12, 6255 (2022)
Bone marrow megakaryocytes (MKs) undergo a maturation involving contacts with the microenvironment before extending proplatelets through sinusoids to deliver platelets in the bloodstream. We demonstrated that MKs assemble linear F-actin-enriched podosomes on collagen I fibers. Microscopy analysis evidenced an inverse correlation between the number of dot-like versus linear podosomes over time. Confocal videomicroscopy confirmed that they derived from each-other. This dynamics was dependent on myosin IIA. Importantly, MKs progenitors expressed the Tks4/5 adaptors, displayed a strong gelatinolytic ability and did not form linear podosomes. While maturing, MKs lost Tks expression together with digestive ability. However, those MKs were still able to remodel the matrix by exerting traction on collagen I fibers through a collaboration between GPVI, ß1 integrin and linear podosomes. Our data demonstrated that a change in structure and composition of podosomes accounted for the shift of function during megakaryopoiesis. These data highlight the fact that members of the invadosome family could correspond to different maturation status of the same entity, to adapt to functional responses required by differentiation stages of the cell that bears them.
REVIEWS
You will find below my reviews
Viaud J, Mansour R, Antkowiak A, Mujalli A, Valet C, Chicanne G, Xuereb J-M, Terrisse A-D, Séverin S, Gratacap M-P, Gaits-Iacovoni F, Payrastre B. Biochimie 2016; 125: 250–8
By interacting specifically with proteins, phosphoinositides organize the spatiotemporal formation of protein complexes involved in the control of intracellular signaling, vesicular trafficking and cytoskeleton dynamics. A set of specific kinases and phosphatases ensures the production, degradation and inter-conversion of phosphoinositides to achieve a high level of precision in the regulation of cellular dynamics coordinated by these lipids. The direct involvement of these enzymes in cancer, genetic or infectious diseases, and the recent arrival of inhibitors targeting specific phosphoinositide kinases in clinic, emphasize the importance of these lipids and their metabolism in the biomedical field.
Boiero Sanders M, Antkowiak A, Michelot A. Open Biol. 2020 Sep;10(9):200157
The actin cytoskeleton has the particularity of being assembled into many functionally distinct filamentous networks from a common reservoir of monomeric actin. Each of these networks has its own geometrical, dynamical and mechanical properties, because they are capable of recruiting specific families of actin-binding proteins (ABPs), while excluding the others. This review discusses our current understanding of the underlying molecular mechanisms that cells have developed over the course of evolution to segregate ABPs to appropriate actin networks. Segregation of ABPs requires the ability to distinguish actin networks as different substrates for ABPs, which is regulated in three different ways: (1) by the geometrical organization of actin filaments within networks, which promotes or inhibits the accumulation of ABPs; (2) by the identity of the networks' filaments, which results from the decoration of actin filaments with additional proteins such as tropomyosin, from the use of different actin isoforms or from covalent modifications of actin; (3) by the existence of collaborative or competitive binding to actin filaments between two or multiple ABPs. This review highlights that all these effects need to be taken into account to understand the proper localization of ABPs in cells, and discusses what remains to be understood in this field of research.
UNPUBLISHED WORK
The work below is in progress
Antkowiak A, Le Goff T, Guillotin A, Michelot A. To be submitted soon..
This project is not yet published. A poster summarizes my approach.
In the cytoplasm of all cells, several actin networks coexist with distinct sizes, geometries, and protein compositions. These parameters give a specific identity to the actin networks which is major to achieve their specific functions (endocytosis, migration, division, etc.). How do some actin binding proteins localize specifically to a given actin network?
To answer this question, we use two complementary approaches, both theoretical and experimental, by using computational models and minimal reconstituted systems.
