SummarySeptins are a large, evolutionarily conserved family of GTPases that form hetero-oligomers and interact with the actin-based cytoskeleton and microtubules. They are involved in scaffolding functions, and form diffusion barriers in budding yeast, the sperm flagellum and the base of primary cilia of kidney epithelial cells. We investigated the role of septins in the primary cilium of retinal pigmented epithelial (RPE) cells, and found that SEPT2 forms a 1:1:1 complex with SEPT7 and SEPT9 and that the three members of this complex colocalize along the length of the axoneme. Similar to observations in kidney epithelial cells, depletion of cilium-localized septins by siRNA-based approaches inhibited ciliogenesis. MAP4, which is a binding partner of SEPT2 and controls the accessibility of septins to microtubules, was also localized to the axoneme where it appeared to negatively regulate ciliary length. Taken together, our data provide new insights into the functions and regulation of septins and MAP4 in the organization of the primary cilium and microtubule-based activities in cells.

Retinitis pigmentosa (RP) is a genetically heterogeneous retinal degeneration characterized by photoreceptor death, which results in visual failure. Here, we used a combination of homozygosity mapping and exome sequencing to identify mutations in ARL2BP, which encodes an effector protein of the small GTPases ARL2 and ARL3, as causative for autosomal-recessive RP (RP66). In a family affected by RP and situs inversus, a homozygous, splice-acceptor mutation, c.101-1G>C, which alters pre-mRNA splicing of ARLBP2 in blood RNA, was identified. In another family, a homozygous c.134T>G (p.Met45Arg) mutation was identified. In the mouse retina, ARL2BP localized to the basal body and cilium-associated centriole of photoreceptors and the periciliary extension of the inner segment. Depletion of ARL2BP caused cilia shortening. Moreover, depletion of ARL2, but not ARL3, caused displacement of ARL2BP from the basal body, suggesting that ARL2 is vital for recruiting or anchoring ARL2BP at the base of the cilium. This hypothesis is supported by the finding that the p.Met45Arg amino acid substitution reduced binding to ARL2 and caused the loss of ARL2BP localization at the basal body in ciliated nasal epithelial cells. These data demonstrate a role for ARL2BP and ARL2 in primary cilia function and that this role is essential for normal photoreceptor maintenance and function.

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Arrestins are dynamic proteins which move between cell compartments triggered by stimulation of G-protein-coupled receptors. Even more dynamically in vertebrate photoreceptors, arrestin1 (Arr1) moves between the inner and outer segments according to the lighting conditions. Previous studies have shown that the light-driven translocation of Arr1 in rod photoreceptors is initiated by rhodopsin through a phospholipase C/protein kinase C (PKC) signaling cascade. The purpose of this study is to identify the PKC substrate that regulates the translocation of Arr1. Mass spectrometry was used to identify the primary phosphorylated proteins in extracts prepared from PKC-stimulated mouse eye cups, confirming the finding with in vitro phosphorylation assays. Our results show that BBS5 is the principal protein phosphorylated either by phorbol ester stimulation or by light stimulation of PKC. Via immunoprecipitation of BBS5 in rod outer segments, Arr1 was pulled down; phosphorylation of BBS5 reduced this co-precipitation of Arr1. Immunofluorescence and immunoelectron microscopy showed that BBS5 principally localizes along the axonemes of rods and cones, but also in photoreceptor inner segments, and synaptic regions. Our principal findings in this study are three-fold. First, we demonstrate that BBS5 is post-translationally regulated by phosphorylation via PKC, an event that is triggered by light in photoreceptor cells. Second, we find a direct interaction between BBS5 and Arr1, an interaction that is modulated by phosphorylation of BBS5. Finally, we show that BBS5 is distributed along the photoreceptor axoneme, co-localizing with Arr1 in the dark. These findings suggest a role for BBS5 in regulating light-dependent translocation of Arr1 and a model describing its role in Arr1 translocation is proposed.

The one-pot sulfonylation/aminoalkylation of styrene derivatives furnishing substituted γ-sulfonylamines was accomplished through a photoredox-catalyzed four-component reaction. Besides one molecule of water and the sodium counterion of the sulfinate, all atoms of the starting materials are transferred to the final product, rendering this process highly atom-efficient. The operationally simple protocol allows for the simultaneous formation of three new single bonds (C–S, C–N, and C–C) and therefore grants rapid access to structurally diverse products.

Shunts, alternative pathways in chemical reaction networks (CRNs), are ubiquitous in nature, enabling adaptability to external and internal stimuli. We introduce a CRN in which the recovery of Michael-accepting species is driven by oxidation chemistry. Using weak oxidants can enable access to two shunts within this CRN with different kinetics and a reduced number of side reactions compared to the main cycle that is driven by strong oxidants. Furthermore, we introduce a strategy to recycle one of the main products under flow conditions to partially reverse the CRN and control product speciation throughout time. These findings introduce new levels of control over artificial CRNs, driven by redox chemistry, narrowing the gap between synthetic and natural systems.

The one-pot sulfonylation/aminoalkylation of styrene derivatives furnishing highly substituted gamma-sulfonylamines was accomplished through a photoredox-catalyzed four-component reaction. Apart from one molecule of water and the sodium counterion of the sulfinate, all atoms of the starting materials are transferred to the final product, rendering this process highly atom-efficient. The operationally simple protocol allows for the simultaneous formation of three new single bonds (C–S, C–N, and C–C) and therefore grants rapid access to structurally diverse products. The reaction proceeds under mild conditions in aqueous acetonitrile and shows a broad scope, including natural products and drug-like molecules.

The one-pot sulfonylation/aminoalkylation of styrene derivatives furnishing highly substituted gamma-sulfonylamines was accomplished through a photoredox-catalyzed four-component reaction. Apart from one molecule of water and the sodium counterion of the sulfinate, all atoms of the starting materials are transferred to the final product, rendering this process highly atom-efficient. The operationally simple protocol allows for the simultaneous formation of three new single bonds (C–S, C–N, and C–C) and therefore grants rapid access to structurally diverse products. The reaction proceeds under mild conditions in aqueous acetonitrile and shows a broad scope, including natural products and drug-like molecules.