📰 Structural convergence between inhibitors and a regulator of microtubule dynamics

Microtubules are fibers of the cytoskeleton whose assembly dynamics are regulated by different families of proteins. They are also the target of small compounds, some of which are used clinically. In a study published in the journal PNASthe scientists showed that a region of the protein (A protein is a biological macromolecule composed of one or more…) CPAP and metabolites produced by bacteria (Bacteria (Bacteria) are prokaryotic unicellular living organisms, characterized…) or fungi shared a common tubulin-binding mode. These results provide one of the first demonstrations of a convergence (The term convergence is used in many fields:) structural relationship between exogenous inhibitors and a cellular regulator of dynamic (The word dynamic is often used to designate or qualify what relates to movement. It…) microtubules.

Microtubules are dynamic assemblies that provide functions vital (The Vitales are an order of dicotyledonous plants. This order has been reintroduced…) in eukaryotic organisms, for example during the division (Division is a law of composition which associates the product of the first with two numbers…) cell, for the establishment of cilia and flagella, or in intracellular traffic. To perform these different functions, microtubules rearrange to form different types of dynamic networks, such as the microtubule « aster » of interphase cells or the mitotic spindle of dividing cells.

Microtubules also form well-defined, more stable structures, such as centrioles. Microtubule dynamics is an intrinsic property of the alpha-beta heterodimer of tubulin, which is the constituent protein of microtubules; however, it is regulated in the cell by different families of proteins. This is the case of the CPAP protein which control (The word control can have several meanings. It can be used as a synonym of examination, of…) the length (The length of an object is the distance between its two furthest extremities…) centriole microtubules. The dynamics of microtubules is also the target of small exogenous compounds, some of which are drugs used in particular in chemotherapy (Chemotherapy is the use of certain chemical substances to treat a disease….) anti-cancer. In general, the question whether the binding sites of cellular partners of tubulin are also the target of small inhibitory compounds still remains unexplored.

One of the methods of choice for answering this type of question is X-ray crystallography. This method requires crystallizing theobject (In general, the word object (from the Latin objectum, 1361) designates an entity defined in…) to analyze. In the case of tubulin, its self-association in heterogeneous assemblies is a brake (A brake is a system that slows down, or even immobilizes, moving parts…) to its crystallization. A method to circumvent this problem is to use tubulin protein ligands which will prevent this self-association. But at the start of this project (A project is an irreversible commitment of uncertain result, not reproducible to…) in 2004, researchers did not have such a protein capable of forming ternary assemblies with tubulin and CPAP.

To better characterize theinteraction (An interaction is an exchange of information, affects or energy between two agents within…) of tubulin with CPAP, and in particular with its PN2-3 domain which has been identified to bind to tubulin, scientists have taken advantage of the recent selection of artificial proteins, called alphaReps, for their ability to bind to tubulin. tubulin-alpha, away from the presumed site of PN2-3. They thus crystallized alphaRep:tubulin:PN2-3 complexes and determined their structure. The results indicate that the N-terminal part of PN2-3 binds to the « vinca » site of tubulin. This site is so named because it is the target of drugs anticancer (An anticancer drug is a medicine used to fight cancer) of the vinca alkaloid family, which includes vinblastine (a molecule (A molecule is an electrically neutral chemical assembly of at least two atoms, which…) from Madagascar periwinkle). It is also the site of attachment of pseudo-peptide compounds produced by bacteria or fungi and which inhibit cell division. Remarkably, the mode of tubulin binding of this region of CPAP and these metabolites is very similar.

These results provide one of the first demonstrations of a structural convergence between small exogenous inhibitors and a cellular regulator of microtubule dynamics. Beyond these fundamental aspects, this work could serve as a guide for the design of new compounds aimed at therapeutic (Therapeutics (from the Greek therapeuein, to cure) is the part of medicine that…) targeting microtubule dynamics.

To know more:
Structural convergence for tubulin binding of CPAP and vinca domain microtubule inhibitors.
Campanacci V, Urvoas A, Ammar Khodja L, Aumont-Nicaise M, Noiray M, Lachkar S, Curmi PA, Minard P, Gigant B.
Proc Natl Acad Sci US A. May 10, 2022 May doi: 10.1073/pnas.2120098119

Laboratory:
Institute of biology (Biology, commonly called « bio », is the science of life….) integration of the cell (I2BC) (CNRS/Paris-Saclay University/CEA) – 1 Avenue (An avenue is a large urban road. It is in principle planted with trees, and leads to a…) from the Terrace. 91190 Gif-sur-Yvette.

Contact:
Benoit Gigant – Searcher (A researcher (fem. researcher) refers to a person whose job is to do research…) CNRS (The National Center for Scientific Research, better known by its acronym CNRS, is the largest…) at theInstitute (An institute is a permanent organization created for a certain purpose. It is…) of Integrative Cell Biology (I2BC) – benoit.gigant at i2bc.paris-saclay.fr