The ANC-1 (Nesprin-1/2) organelle-anchoring protein functions through mitochondria to polarize axon growth in response to SLT-1

Abstract

A family of giant KASH proteins, including C. elegans ANC-1 and mammalian Nesprin-1 and -2, are involved in organelle anchoring and are associated with multiple neurodevelopmental disorders including autism, bipolar disorder, and schizophrenia. However, little is known about how these proteins function in neurons. Moreover, the role of organelle anchoring in axon development is poorly understood. Here, we report that ANC-1 functions with the SLT-1 extracellular guidance cue to polarize ALM axon growth. This role for ANC-1 is specific to its longer ANC-1A and ANC-1C isoforms, suggesting that it is mechanistically distinct from previously described roles for ANC-1. We find that ANC-1 is required for the localization of a cluster of mitochondria to the base of the proximal axon. Furthermore, genetic and pharmacological studies indicate that ANC-1 functions with mitochondria to promote polarization of ALM axon growth. These observations reveal a mechanism whereby ANC-1 functions through mitochondria to polarize axon growth in response to SLT-1.

Principles of organelle positioning in motile and non-motile cells

“…Next to these conceptual gaps of knowledge, research on the underexplored topic of organelle positioning may well lead to surprises in the employed molecular mechanisms, such as findings showing that different cytoskeletal protein isoforms may have different roles in organelle positioning (Roman et al, 2017 ) and recent findings suggesting that the LINC complex protein ANC-1 in C- elegans is not only required for nuclear positioning but also for positioning of the ER, mitochondria, and lipid droplets (Hao et al, 2021 ; Fischer et al, 2022 ). Additionally, we are only at the beginning of understanding how asymmetric patterns of posttranslational modifications of cytoskeleton components like microtubules (Lavrsen et al, 2023 ; Janke and Magiera, 2020 ) influence organelle localisation, such as the recently identified role of polyglutamylated microtubules in ER and lysosome positioning (Zheng et al, 2022 ).…”

Autism candidate generbm-26(RBM26/27) regulates MALS-1 to protect against mitochondrial dysfunction and axon degeneration during neurodevelopment.

“…Beading refers to focal enlargement or bubblelike lesions which were at least twice the diameter of the axon in size as shown in Figure S3. Imaging: Larval stage images displayed in all figures were obtained by mounting on 5% agarose pad, anesthetizing with levamisole, and imaging with a 60x water objective on a Nikon ECLIPSE Ti microscope equipped with the X-Light V2 L-FOV spinning disk system as previously described [58]. NIS-Elements software was used for image acquisition.…”

“…Corrected total pixel/area was obtained by subtracting the background pixel/area from the ROI for both red and green channels. Auxin mediated protein degradation: Tissue-specific degradation of RBM-26::Scarlet::AID was carried out using the auxin-induced degron (AID) system as previously described [58]. Briefly, Naphthaleneacetic acid (K-NAA) (Phytotechnology Laboratories) was dissolved in double distilled water to obtain 250 mM K-NAA solution and filter-sterilized by passing through 25 mm sterile syringe filter (Pall Corporation).…”

Active Microtubule-Actin Crosstalk Mediated by a Nesprin-2G-Kinesin Complex

“…It also plays important roles in chromosome pairing during meiosis (7,8). In the nematode Caenorhabditis elegans, KASH proteins are required for positioning of nuclei as well as proper organelle positioning within cells (9)(10)(11)(12). Several human diseases, including ataxias, amyotrophic lateral sclerosis, cardiomyopathies, deafness, and Emery-Dreifuss muscular dystrophy are associated with mutations in nesprin-encoding genes (13).…”