MTUS2

MTUS2 (TIP150) is a microtubule plus-end tracking protein (+TIP) that couples plus-end machinery to chromosome segregation, entosis, and directional cell migration (PMID:19543227, PMID:24847103, PMID:27451391). It is recruited to growing microtubule plus ends through direct binding to EB1, where it assembles as a tetramer engaging an EB1 dimer via its C-terminal domain; EB1 is required for TIP150 plus-end targeting (PMID:19543227, PMID:23595990). Once localized, TIP150 directly binds the microtubule depolymerase MCAK and drives its EB1-dependent loading onto plus ends (PMID:19543227). This EB1–TIP150–MCAK module is dynamically regulated: Aurora B phosphorylation dissolves the TIP150–MCAK association, Aurora A phosphorylation of MCAK perturbs the intramolecular MCAK conformation needed for TIP150 binding, and PCAF-mediated acetylation of EB1 disrupts the TIP150–EB1 interface — perturbation of these interactions impairs metaphase chromosome alignment and activates the spindle checkpoint (PMID:19543227, PMID:23595990, PMID:24847103). The three proteins further compartmentalize the kinetochore–microtubule machinery by undergoing liquid–liquid phase separation at plus ends, which acetylation of EB1 Lys220 attenuates (PMID:38323478). Through a distinct C-terminal proline-rich region binding the cortactin SH3 domain at the cortical cytoskeleton, TIP150 also supports polarized cell migration, an interaction negatively regulated by EGF-driven cortactin tyrosine phosphorylation (PMID:27451391).

1. 2009 High

   Established MTUS2/TIP150 as a bona fide +TIP and identified EB1 as the recruiting factor, defining how the protein reaches microtubule plus ends.

   Evidence In vitro EB1 binding, plus-end co-localization, and EB1 siRNA knockdown

   PMID:19543227

   Open questions at the time

   • Did not define the structural EB1-binding motif resolved later
   • No functional consequence of plus-end targeting yet established
2. 2009 High

   Showed TIP150 directly binds and loads the depolymerase MCAK at plus ends, linking the +TIP to control of microtubule dynamics.

   Evidence In vitro binding plus TIP150 knockdown with MCAK localization readout

   PMID:19543227

   Open questions at the time

   • Quantitative effect on depolymerization kinetics not measured
   • Cellular phenotype of disrupted loading not yet defined
3. 2009 Medium

   Identified Aurora B phosphorylation as a switch dissolving the TIP150-MCAK interaction, the first regulatory input on the module.

   Evidence In vitro kinase assay followed by binding assay

   PMID:19543227

   Open questions at the time

   • Phosphosites not mapped in vivo
   • Single lab in vitro reconstitution without cellular validation
4. 2013 High

   Resolved the oligomeric architecture (TIP150 tetramer binding an EB1 dimer) and demonstrated that disrupting this interface arrests mitosis, establishing the interaction as essential for chromosome segregation.

   Evidence Oligomerization analysis, Co-IP, dominant-negative peptide and siRNA with mitotic phenotype

   PMID:23595990

   Open questions at the time

   • No atomic structure of the tetramer-dimer interface
   • Stoichiometry at native plus ends in vivo not directly quantified
5. 2013 High

   Defined PCAF acetylation of EB1 as a second regulatory layer disrupting TIP150-EB1 binding and perturbing chromosome alignment, with BubR1 epistasis linking it to checkpoint control.

   Evidence In vitro acetylation, Co-IP, BubR1 siRNA epistasis, live-cell imaging

   PMID:23595990

   Open questions at the time

   • Endogenous acetylation dynamics during mitosis not tracked
   • Upstream signals controlling PCAF activity unknown
6. 2014 High

   Extended the TIP150-MCAK module to entosis and showed Aurora A regulates an MCAK intramolecular conformation required for TIP150 binding, connecting plus-end dynamics to cell mechanical rigidity.

   Evidence Intramolecular association assay, in vitro kinase assay, Co-IP, optical trap, live-cell entosis assay

   PMID:24847103

   Open questions at the time

   • Mechanistic link between plus-end dynamics and cortical rigidity not fully resolved
   • Aurora A phosphosites on MCAK in this context not mapped
7. 2016 High

   Identified a cortactin SH3-binding function for TIP150's C-terminal proline-rich region, establishing a microtubule-independent role in polarized cell migration regulated by EGF signaling.

   Evidence Co-IP, in vitro binding, TAT-CT150 peptide perturbation, siRNA, directional migration assay

   PMID:27451391

   Open questions at the time

   • Cortactin tyrosine phosphosites mediating regulation not pinpointed
   • Relationship between cortical and plus-end pools of TIP150 unresolved
8. 2024 High

   Demonstrated that EB1, TIP150, and MCAK form phase-separated condensates at plus ends, providing a biophysical organizing principle for the kinetochore-MT machinery sensitive to EB1 acetylation.

   Evidence In vitro droplet phase-separation assay, competing peptide in cells and Drosophila embryos, EB1 acetylation mutagenesis, live-cell imaging

   PMID:38323478

   Open questions at the time

   • In vivo evidence that endogenous condensates form at native plus ends remains indirect
   • Material properties and turnover of condensates not characterized

• The developmental and tissue-specific functions of MTUS2 implied by its embryonic cardiac and neural expression remain mechanistically unconnected to its characterized +TIP roles.
• No organismal phenotype links MTUS2 isoforms to cardiac or neural development
• Functional difference between the 358- and 1354-aa isoforms uncharacterized