Abstract
Axons and dendrites are long extensions of neurons that contain arrays of noncentrosomal microtubules. Calmodulin-regulated spectrin-associated proteins (CAMSAPs) bind to and stabilize free microtubule minus ends and are critical for proper neuronal development and function. Previous studies have shown that the microtubule-severing ATPase katanin interacts with CAMSAPs and limits the length of CAMSAP-decorated microtubule stretches. However, how CAMSAP and microtubule minus end dynamics are regulated in neurons is poorly understood. Here, we show that the neuron-enriched protein WDR47 interacts with CAMSAPs and is critical for axon and dendrite development. We find that WDR47 accumulates at CAMSAP2-decorated microtubules, is essential for maintaining CAMSAP2 stretches, and protects minus ends from katanin-mediated severing. We propose a model where WDR47 protects CAMSAP2 at microtubule minus ends from katanin activity to ensure proper stabilization of the neuronal microtubule network.
Highlights
In neurons, several processes, such as migration, polarization, plasticity, and development, rely on proper organization of the microtubule (MT) cytoskeleton
WDR47 was detected during early neuronal development in lysates harvested at days in vitro (DIV) 1–2, increased $2-fold at DIV4 and DIV7, a period characterized by axonal growth, and reached an $3-fold increase around DIV14–DIV21, when dendrites develop (Figures 1A and 1B)
Upon close examination of DIV4 neuronal morphology, we found that WDR47 depletion impaired axonal growth because total axon length was decreased significantly compared with controls (Figures 1D and 1E)
Summary
Several processes, such as migration, polarization, plasticity, and development, rely on proper organization of the microtubule (MT) cytoskeleton. MTs provide structural support to ensure specialized cell morphology, act as scaffolds for organelle positioning, and facilitate intracellular transport, for which molecular motors recognize and use the intrinsic polarity of MTs to transport cargo in a directional manner (Conde and Caceres, 2009; Kapitein and Hoogenraad, 2015) This intrinsic polarity results in MTs having two structurally and functionally different ends, the plus and minus end, that each display distinct behavior in living cells. Our understanding of MT minus end dynamics advanced substantially with discovery of the calmodulin-regulated spectrin-associated protein (CAMSAP) family of proteins, which associate with MT minus ends. This function was initially characterized for Nezha/CAMSAP3, which binds MT minus ends and tethers them to adherens junctions (Meng et al, 2008). Little is known about the role of katanin in regulation of CAMSAPs at MT minus ends in neurons
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