EB3 regulates microtubule dynamics at the cell cortex and is required for myoblast elongation and fusion.
During muscle differentiation, myoblasts elongate and fuse into syncytial myotubes [1]. An early event during this process is the remodeling of the microtubule cytoskeleton, involving disassembly of the centrosome and, crucially, the alignment of microtubules into a parallel array along the long axis of the cell [2-5]. To further our understanding on how microtubules support myogenic differentiation, we analyzed the role of EB1-related microtubule-plus-end-binding proteins. We demonstrate that EB3 [6] is specifically upregulated upon myogenic differentiation and that knockdown of EB3, but not that of EB1, prevents myoblast elongation and fusion into myotubes. EB3-depleted cells show disorganized microtubules and fail to stabilize polarized membrane protrusions. Using live-cell imaging, we show that EB3 is necessary for the regulation of microtubule dynamics and microtubule capture at the cell cortex. Expression of EB1/EB3 chimeras on an EB3-depletion background revealed that myoblast fusion depends on two specific amino acids in the calponin-like domain of EB3, whereas the interaction sites with Clip-170 and CLASPs are dispensable. Our results suggest that EB3-mediated microtubule regulation at the cell cortex is a crucial step during myogenic differentiation and might be a general mechanism in polarized cell elongation.
Wellcome Trust Centre for Cell Biology, University of Edinburgh, King's Buildings, Edinburgh, Scotland, UK. a.straube@mcri.ac.uk
Anne
A
Straube
Andreas
A
Merdes
D000595:Amino Acid Sequence; D000818:Animals; D019556:COS Cells; D002454:Cell Differentiation; D002459:Cell Fusion; D002460:Cell Line; D002522:Chlorocebus aethiops; D005109:Extracellular Matrix / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D051379:Mice; D008869:Microtubule-Associated Proteins / Q000737:chemistry / Q000378:metabolism*; D008870:Microtubules / Q000378:metabolism*; D008969:Molecular Sequence Data; D032446:Myoblasts / Q000166:cytology* / Q000378:metabolism; D017434:Protein Structure, Tertiary; D017385:Sequence Homology
D008869:Microtubule-Associated Proteins