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

Abstract

Recent studies have revealed the presence of a microtubule subpopulation called Golgi-derived microtubules that support Golgi ribbon formation, which is required for maintaining polarized cell migration. CLASPs and AKAP450/CG-NAP are involved in their formation, but the underlying molecular mechanisms remain unclear. Here, we find that the microtubule-crosslinking protein, MTCL1, is recruited to the Golgi membranes through interactions with CLASPs and AKAP450/CG-NAP, and promotes microtubule growth from the Golgi membrane. Correspondingly, MTCL1 knockdown specifically impairs the formation of the stable perinuclear microtubule network to which the Golgi ribbon tethers and extends. Rescue experiments demonstrate that besides its crosslinking activity mediated by the N-terminal microtubule-binding region, the C-terminal microtubule-binding region plays essential roles in these MTCL1 functions through a novel microtubule-stabilizing activity. These results suggest that MTCL1 cooperates with CLASPs and AKAP450/CG-NAP in the formation of the Golgi-derived microtubules, and mediates their development into a stable microtubule network.

A regulatory subunit of protein phosphatase 2A, PPP2R5E, regulates the abundance of microtubule crosslinking factor 1

“…The lysate from Flag-tagged fulllength MTCL1-expressing 293T cells was subjected to immunoprecipitation with anti-Flag antibody and the immunoprecipitated proteins were eluted using Flag peptide followed by identification using mass spectrometry. As reported previously [7,8], we found that CLASPs and PAR-1 (MARK) were associated with MTCL1 ( Fig. 1A).…”

“…A). The disruption of MT organization appears to be more drastic than in previous reports , which may have resulted from the difference of cell lines. The previous study used HeLa–Kyoto cells, whereas our studies were performed using authentic HeLa cells.…”

“…In addition, MTCL1 promoted the recruitment of the evolutionarily conserved cell polarity-regulating kinase, partitioning-defective 1 (PAR-1), for the development of apicobasal MT bundles [7]. MTCL1 was also shown to associate with cytoplasmic linker associated proteins (CLASPs) and AKAP450/CG-NAP at the Golgi membrane [8]. This association was essential for the recruitment of MTCL1 to the Golgi apparatus, where MTCL1 stabilized and developed Golginucleated MTs [8].…”

Genetic loci associated with chronic obstructive pulmonary disease overlap with loci for lung function and pulmonary fibrosis

“…As eQTL are pervasive, we also attempted to determine whether our association signal co-localized 23 with an eQTL signal in lung tissue (Supplementary Table 9). We found strong evidence of co-localization (posterior probability > 0.8) for DSP , a major protein of desmosomes required for epidermal integrity 24 , and MTCL1 , important in epithelial-cell-specific microtubule stabilization 25,26 , and expressed in respiratory epithelial cells 27 . Variants in strong LD with our top MTCL1 variant rs647097 (NC_000018.9:g.8808464T>C) appear to have enhancer histone marks in fetal lung fibroblasts 28,29 .…”

Golgi ribbon disassembly during mitosis, differentiation and disease progression

“…In support of microtubule growth from the Golgi, the core component and modulators of the microtubule-nucleating y-tubulin ring complexes (γ-TuRCs), including γ-tubulin, AKAP450, Cdk5Rap2 and myomegalin, have been found localized to Golgi membranes where they collaborate to initiate microtubule nucleation [38–40,20]. Moreover, microtubule-associated proteins (MAPs), such as the minus-end binding protein CAMSAP2 and the plus-end tracking proteins CLASPs that recruits the microtubule-crosslinking protein MTCL1 to the Golgi, also help anchor and stabilize Golgi-derived microtubules and thus contribute to Golgi organization and function [36,41,42*]. …”