MICROTUBULE PLUS END · Structural and kinetic basis of evolutionary conserved and divergent microtubule plus end tracking mechanisms
FP7 — People (Marie Curie Actions)
- Duration
- 2011-01-01 → 2012-12-31
- EU contribution
- €172,241
- Participants
- 1
- Scheme
- MC-IEF
Lines connect the coordinator with its partners.
Results in brief
Structural and kinetic basis of evolutionary conserved and divergent microtubule plus end tracking mechanisms
Introduction The microtubule cytoskeleton is of crucial importance for many essential cellular functions such as establishing cell morphology, intracellular transport, chromosome segregation during cell division and cell motility. Failures in these processes can result in promotion of cancer and developmental diseases. Microtubules are structurally polar tubes made of protofilaments assembled from proteins called alpha / beta-tubulin. Tubulin is incorporated into microtubules with guanosine triphosphate proteins (GTP) bound to its beta-subunit. During microtubule assembly GTP is hydrolysed; this reaction is ultimately responsible for the property of microtubules to randomly switch between phases of growth and shrinkage, a behaviour termed dynamic instability. It is essential for the ability of microtubules to explore intracellular space, to rapidly reorganise their distribution and to contribute to generating the pushing and pulling forces that move chromosomes during cell division. Critical decisions between microtubule assembly and disassembly take place at microtubule ends. End-binding proteins (EBs) bind there to a region with so far unknown structural characteristics. EBs recruit a variety of other factors, thereby constituting the core of a versatile protein interaction network, which allows the cell to shape and control their microtubule cytoskeleton. Results To better understand how EBs interact with microtubule ends, we examined the structural characteristics of this interaction. Using cryo-electron microscopy, subnanometre single-particle reconstruction, and fluorescence microscopy imaging, we discovered that EBs bridge microtubule protofilaments at a position that is right next to the beta-tubulin GTPase site. That is of interest, because this binding site positions them ideally to sense GTP hydrolysis. We further found that the region recognised by EBs functions as a stabilising structural cap which protects microtubules from disassembly, thus allowing them to have extended episodes of continuous growth. Taken together, our findings establish a structural link between two important biological phenomena, microtubule dynamic instability and microtubule end tracking by EBs.
Data: CORDIS, © European Union
Project objective
In eukaryotic cells the microtubule (MT) cytoskeleton is of crucial importance for many essential cellular functions. The determination of cell morphology, intracellular transport, chromosome segregation in mitosis, and cell motility belong to the processes carried out by MTs. Aberrant cell morphology, developmental diseases and promotion of malignant transformations in animal cells are results of failures in these processes. The dynamically growing plus end of MTs is of special interest as it serves as a cellular hub integrating signals needed to regulate the MT cytoskeleton and its functions. Due to the plus end’s highly dynamic nature and the complexity of protein-protein interactions at the end, it is still unclear which structural transitions take place at microtubule ends and which structures are recognized by regulatory proteins that bind the growing ends selectively. This project aims at a mechanistic understanding of selective targeting of specialized proteins to microtubule ends that exhibit diverse functions there. Two layers of interactions at microtubule ends are addressed in this proposal: (1) We aim to elucidate the molecular origin for the conserved property of end binding proteins (EBs) to bind autonomously to the growing microtubule plus end region, which provides a dynamic platform for second-layer binding of more divergent proteins. (2) We aim to understand the logics underlying the less conserved interactions of these other microtubule associated proteins (MAPs) with EB-decorated MT ends. These two layers of the MT plus-end binding protein interaction network will be analyzed by a concerted, multidisciplinary experimental approach combining in vitro and in vivo experiments, using quantitative fluorescence microscopy to measure the dynamics of MT end tracking and electron microscopy to gain insight into the structural origin of function.
Original text from CORDIS.
Participants
- CANCER RESEARCH UK LBG · LONDONCoordinatorUnited Kingdom
Links
Data: CORDIS, © European Union