NOCA-1 functions with γ-tubulin and in parallel to Patronin to assemble non-centrosomal microtubule arrays in C. elegans

Abstract

Non-centrosomal microtubule arrays assemble in differentiated tissues to perform mechanical and transport-based functions. In this study, we identify Caenorhabditis elegans NOCA-1 as a protein with homology to vertebrate ninein. NOCA-1 contributes to the assembly of non-centrosomal microtubule arrays in multiple tissues. In the larval epidermis, NOCA-1 functions redundantly with the minus end protection factor Patronin/PTRN-1 to assemble a circumferential microtubule array essential for worm growth and morphogenesis. Controlled degradation of a γ-tubulin complex subunit in this tissue revealed that γ-tubulin acts with NOCA-1 in parallel to Patronin/PTRN-1. In the germline, NOCA-1 and γ-tubulin co-localize at the cell surface, and inhibiting either leads to a microtubule assembly defect. γ-tubulin targets independently of NOCA-1, but NOCA-1 targeting requires γ-tubulin when a non-essential putatively palmitoylated cysteine is mutated. These results show that NOCA-1 acts with γ-tubulin to assemble non-centrosomal arrays in multiple tissues and highlight functional overlap between the ninein and Patronin protein families.DOI: http://dx.doi.org/10.7554/eLife.08649.001

Noncentrosomal microtubules in C. elegans epithelia

“…First, NOCA-1 and g-tubulin co-localise at the level of junctions in the seam cells and form puncta in epidermal cells (Fig. 1), whereas PTRN-1 only shows a punctate epidermal pattern (Wang et al, 2015). Second, while PTRN-1 or NOCA-1 single loss of function moderately affects MT bundle density, their combined inactivation strongly reduces it with consequences on the larval epidermal integrity and viability.…”

“…In C. elegans (see Box 1 for the composition of C. elegans MTs, Box 2 for tools to study them), this re-localization has been observed in the epidermis, the intestine, as well as in the germline (Feldman and Priess, 2012;Quintin et al, 2015;Wang et al, 2015). In the embryonic epidermis, g-tubulin switches from a dotty centrosomal signal to a noncentrosomal location at the cell surface, along hemidesmosome-like junctions (which anchor epidermal cells to the extracellular matrix that separates them from the underlying muscles), or along cell-cell junctions (Fig.…”

“…In the embryonic epidermis, g-tubulin switches from a dotty centrosomal signal to a noncentrosomal location at the cell surface, along hemidesmosome-like junctions (which anchor epidermal cells to the extracellular matrix that separates them from the underlying muscles), or along cell-cell junctions (Fig. 1A-F) Quintin et al, 2016;Wang et al, 2015). In the embryonic intestine, g-tubulin and several proteins of the PCM (ZYG-9, TAC-1, AIR-1 and GIP-1, also known as CeGrip-1) re-localize in a two-step mechanism to the apical surface; these proteins subsequently decorate the intestinal lumen, coincidently with a nuclear movement from the cell center to its apex ( Fig.…”

“…MT minus-end binding proteins display stabilizing or protecting activities, and largely contribute to noncentrosomal MT generation. C. elegans possesses three known -TIPs (Box 1): g-tubulin and its associated proteins GIP-1 and GIP-2 (Hannak et al, 2002), PTRN-1 [belonging to the conserved Patronin/ Nehza/calmodulin and spectrin-associated family (CAMSAP) (Goodwin and Vale, 2010)], and NOCA-1(noncentrosomal array 1) with homology to ninein (Wang et al, 2015). PTRN-1 function has mostly been described in neurons (Marcette et al, 2014;Richardson et al, 2014), and axon regeneration (Chuang et al, 2014).…”

“…NOCA-1 was initially identified in the same cluster as g-tubulin and dynein after multiparametric profiling of the results of a screen for germline defects (Green et al, 2011). Recently Wang and collaborators have dissected the respective roles of these three -TIPs in assembling noncentrosomal MTs in the epidermis (Wang et al, 2015). Two arguments strongly suggest that NOCA-1 and g-tubulin act in parallel to PTRN-1 to organize circumferential MT filaments.…”