Doublecortin Recognizes the 13-Protofilament Microtubule Cooperatively and Tracks Microtubule Ends

Abstract

Neurons, like all cells, face the problem that tubulin forms microtubules with too many or too few protofilaments (pfs). Cells overcome this heterogeneity with the γ-tubulin ring complex, which provides a nucleation template for 13-pf microtubules. Doublecortin (DCX), a protein that stabilizes microtubules in developing neurons, also nucleates 13-pf microtubules in vitro. Using fluorescence microscopy assays, we show that the binding of DCX to microtubules is optimized for the lateral curvature of the 13-pf lattice. This sensitivity depends on a cooperative interaction wherein DCX molecules decrease the dissociation rate of their neighbors. Mutations in DCX found in patients with subcortical band heterotopia weaken these cooperative interactions. Using assays with dynamic microtubules, we discovered that DCX binds to polymerization intermediates at growing microtubule ends. These results support a mechanism for stabilizing 13-pf microtubules that allows DCX to template new 13-pf microtubules through associations with the sides of the microtubule lattice.

MTCL1 crosslinks and stabilizes non-centrosomal microtubules on the Golgi membrane

“…9). An intriguing idea is that the KR-rich region of MTCL1 stabilizes MTs by binding to the groove between the MT protofilaments, similarly to EB1 and doublecortin 28,29 . Detailed analysis of the interaction mode between the KR-rich region and a single-MT strand is required to clarify this issue.…”

Tubulin acetylation: responsible enzymes, biological functions and human diseases

“…Paclitaxel) promotes formation of 12-protofilament microtubules [107]. Moreover, the microtubule stabilizing protein doublecortin stimulates assembly of 13-protofilament microtubules in vitro and the intracellular transport motor protein kinesin is also in favor of 13-protofilament microtubules [96,108,109], indicating that microtubule-association proteins directly affect the protofilament number of microtubules.…”

“…3b). Related to this, kinesin and doublecortin affect the protofilament number of microtubules assembled in vitro [96,108,109]. Moreover, deletion of the Mec-17 gene leads to loss of mysterious darkly stained material inside microtubules [112].…”

Doublecortin Recognizes the Longitudinal Curvature of the Microtubule End and Lattice

“…These results provide a plausible mechanism by which EB1 could recognize the GTP cap. Many other proteins autonomously recognize the microtubule end, including the microtubule depolymerase MCAK [20], the polymerase XMAP215 [21], the kinetochore complex Dam1 [22], and the neuronal microtubule-associated protein Doublecortin (DCX) [23]. It remains unclear, however, whether these proteins recognize the same feature of microtubule ends, namely their nucleotide state, as EB1 does.…”