Ankyrin-B is a PI3P effector that promotes polarized α5β1-integrin recycling via recruiting RabGAP1L to early endosomes

Abstract

Endosomal membrane trafficking requires coordination between phosphoinositide lipids, Rab GTPases, and microtubule-based motors to dynamically determine endosome identity and promote long-range organelle transport. Here we report that ankyrin-B (AnkB), through integrating all three systems, functions as a critical node in the protein circuitry underlying polarized recycling of α5β1-integrin in mouse embryonic fibroblasts, which enables persistent fibroblast migration along fibronectin gradients. AnkB associates with phosphatidylinositol 3-phosphate (PI3P)-positive organelles in fibroblasts and binds dynactin to promote their long-range motility. We demonstrate that AnkB binds to Rab GTPase Activating Protein 1-Like (RabGAP1L) and recruits it to PI3P-positive organelles, where RabGAP1L inactivates Rab22A, and promotes polarized trafficking to the leading edge of migrating fibroblasts. We further determine that α5β1-integrin depends on an AnkB/RabGAP1L complex for polarized recycling. Our results reveal AnkB as an unexpected key element in coordinating polarized transport of α5β1-integrin and likely of other specialized endocytic cargos.DOI: http://dx.doi.org/10.7554/eLife.20417.001

Cargo hold and delivery: Ankyrins, spectrins, and their functional patterning of neurons

“…Interestingly, a similar ZU5 N ‐ZU5 C ‐UPA‐DD tandem is present in p53‐inducible death‐domain‐containing protein (PIDD), a scaffolding protein implicated in the regulation of apoptosis in response to DNA damage (Wang et al, ). The only known function for the DD of ankyrins to date is that is required to bind RabGAP1L to inactivate Rab22A and to efficiently recycle α5β1‐integrin dimers to the leading edge of migrating fibroblasts, which promotes haptotaxis on a fibronectin gradient (Qu et al, ). The C‐terminus portion of ankyrins consists of an unstructured regulatory domain, which engages in intramolecular interactions (Chen, Li, Wang, Wei, & Zhang, ; Mohler, Gramolini, & Bennett, ).…”

“…In a departure from their canonical roles as static plasma membrane organizers, members of the ankyrin and spectrin families associate with molecular motors and organelles to facilitate intracellular transport in neurons and other cell types (Lorenzo et al, , , ; Lorenzo & Bennett, ; Muresan et al, ; Qu et al, ; Takeda et al, ). For example, the 220 kDa ankyrin‐B isoform couples the dynactin/dynein motor complex to multiple organelles to promote their retrograde axonal transport (Lorenzo et al, ).…”

A giant ankyrin-B mechanism for neuro-diversity/divergence through stochastic ectopic axon projections

“…ANK2 encodes 2 major ankyrin-B (ankB) polypeptides: one of 220 kDa that is broadly expressed and associated with cardiac arrhythmia 9,10 as well as age-dependent obesity 11,12 , and another of 440 kDa (giant ankB) that is expressed only in neurons and targets to axons (Extended Data Fig.1a) [13][14][15][16][17] . 220-kDa ankB functions in polarized transport of intracellular organelles as a PI3P adaptor that also binds to dynactin 17,18 . Mice lacking both ankyrin polypeptides exhibit a major reduction in long axon tracts including within the corpus callosum 17,19 .…”

βII-spectrin promotes mouse brain connectivity through stabilizing axonal plasma membranes and enabling axonal organelle transport

“…Spectrins and ankyrins also have been implicated in microtubuledependent transport of intracellular organelles (11)(12)(13)(14)(15). The dynein/ dynactin motor complex drives neuronal microtrubule-based transport in the retrograde direction, while a diverse group of kinesin motors move cargo anterogradely (16).…”

“…Expression of Drosophila β-spectrin bearing human βIII-spectrin mutations causing spinocerebellar ataxia type 5 (SCA5) results in impaired neuronal organelle transport in flies (13). AnkB associates with endolysosomal organelles through PI3P lipids and is required for their axonal transport (14) and for polarized recycling of α5/β1 integrin dimers in migrating fibroblasts (15).…”