Patronin Regulates the Microtubule Network by Protecting Microtubule Minus Ends

SummaryTubulin assembles into microtubule polymers that have distinct plus and minus ends. Most microtubule plus ends in living cells are dynamic; the transitions between growth and shrinkage are regulated by assembly-promoting and destabilizing proteins. In contrast, minus ends are generally not dynamic, suggesting their stabilization by some unknown protein. Here, we have identified Patronin (also known as ssp4) as a protein that stabilizes microtubule minus ends in Drosophila S2 cells. In the absence of Patronin, minus ends lose subunits through the actions of the Kinesin-13 microtubule depolymerase, leading to a sparse interphase microtubule array and short, disorganized mitotic spindles. In vitro, the selective binding of purified Patronin to microtubule minus ends is sufficient to protect them against Kinesin-13-induced depolymerization. We propose that Patronin caps and stabilizes microtubule minus ends, an activity that serves a critical role in the organization of the microtubule cytoskeleton.

Graphical AbstractFigure optionsDownload high-quality image (146 K)Download as PowerPoint slideHighlights
► Patronin protects microtubule minus ends from depolymerases in vivo
► Without Patronin, microtubule organization is defective in interphase and mitosis
► In vitro Patronin can protect minus ends from Kinesin-13-catalyzed depolymerization
► Similar to plus ends, stabilizing and destabilizing proteins regulate minus ends