Lens Aquaporin-5 Inserts Into Bovine Fiber Cell Plasma Membranes Via Unconventional Protein Secretion

Gletten, Romell; Cantrell, Lee S.; Bhattacharya, Sujoy; Schey, Kevin L.

doi:10.1167/iovs.63.8.5

Cited by 8 publications

(5 citation statements)

References 72 publications

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“…Intracellular vesicles and the lysosomal membranes were, however, labelled ( Figure 6 ). Both are critical to lens differentiation in organelle removal [ 76 , 77 ] and for aquaporin trafficking by a lysosomal-associated unconventional protein secretion mechanism [ 78 ]. Then the process of lens fibre cell compaction [ 79 ] and the fenestration of lens fibre cells leading to the formation of a stratified syncytium [ 80 ] will require an amphipathic helix containing proteins to be involved.…”

Section: Discussionmentioning

confidence: 99%

Independent Membrane Binding Properties of the Caspase Generated Fragments of the Beaded Filament Structural Protein 1 (BFSP1) Involves an Amphipathic Helix

Jarrı́n

Kalligeraki

Uwineza

et al. 2023

Cells

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Background: BFSP1 (beaded filament structural protein 1) is a plasma membrane, Aquaporin 0 (AQP0/MIP)-associated intermediate filament protein expressed in the eye lens. BFSP1 is myristoylated, a post-translation modification that requires caspase cleavage at D433. Bioinformatic analyses suggested that the sequences 434–452 were α-helical and amphipathic. Methods and Results: By CD spectroscopy, we show that the addition of trifluoroethanol induced a switch from an intrinsically disordered to a more α-helical conformation for the residues 434–467. Recombinantly produced BFSP1 fragments containing this amphipathic helix bind to lens lipid bilayers as determined by surface plasmon resonance (SPR). Lastly, we demonstrate by transient transfection of non-lens MCF7 cells that these same BFSP1 C-terminal sequences localise to plasma membranes and to cytoplasmic vesicles. These can be co-labelled with the vital dye, lysotracker, but other cell compartments, such as the nuclear and mitochondrial membranes, were negative. The N-terminal myristoylation of the amphipathic helix appeared not to change either the lipid affinity or membrane localisation of the BFSP1 polypeptides or fragments we assessed by SPR and transient transfection, but it did appear to enhance its helical content. Conclusions: These data support the conclusion that C-terminal sequences of human BFSP1 distal to the caspase site at G433 have independent membrane binding properties via an adjacent amphipathic helix.

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Section: Discussionmentioning

confidence: 99%

Independent Membrane Binding Properties of the Caspase Generated Fragments of the Beaded Filament Structural Protein 1 (BFSP1) Involves an Amphipathic Helix

Jarrı́n

Kalligeraki

Uwineza

et al. 2023

Cells

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“…For immunofluorescence, bovine lenses were fixed and cryoprotected as described previously. 31 We collected 20-µm sections on regular glass slides in PBS. The sections were washed with PBS and incubated with blocking solution containing 6% BSA and 6% normal goat serum in PBS for 1.5 hours.…”

Section: Methodsmentioning

confidence: 99%

Spatially Resolved Proteomics Reveals Lens Suture-Related Cell–Cell Junctional Protein Distributions

Wang,

Gletten,

Schey

2023

Invest. Ophthalmol. Vis. Sci.

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Purpose Lens transparency relies on the precise organization of lens fiber cells. The formation of the highly ordered lens architecture results from not only cell–cell adhesion along the lateral interfaces, but also from proper organization of fiber cells tips at lens sutures. Little is known about the cell adhesion between fiber tips at the sutures. The purpose of this study is to map suture-specific protein distributions. Methods Tissue sections were obtained from fresh frozen bovine lenses and washes were performed to remove soluble proteins and to retain membrane and membrane associated proteins. Imaging mass spectrometry (IMS) combined with on-tissue trypsin digestion was used to visualize protein spatial distributions. Sutures and adjacent regions were captured by laser capture microdissection and samples were digested by trypsin. Proteins were analyzed by liquid chromatography tandem MS and quantified by label-free quantification. Protein spatial distributions were confirmed by immunofluorescence. Results IMS results showed enrichment of adherens junction proteins cadherin-2 and armadillo repeat gene deleted in velo–cardio–facial syndrome (ARVCF) in both anterior and posterior sutures of bovine lenses. Liquid chromatography tandem MS confirmed higher expression of cadherin-2 and ARVCF and other adherens junction proteins including catenin α2 (CTNNA2) and catenin β1 (CTNNB1) in sutures. In contrast, IMS indicated low expression of gap junction protein connexin 50 and connexin 46 in the suture regions. The localization of cadherin-2 and connexin 50 was confirmed by immunofluorescence. Conclusions The complementary expression of adherens junction proteins and gap junction proteins in lens suture regions implicates adherens junctions in fiber cell tip adhesion and in maintaining the integrity of the lens.

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“…In lens fiber cells, AQP5 plasma membrane insertion occurs over time in contrast to the immediate insertion of AQP0 [ 143 ]. Interestingly, the colocalization of AQP5 with mitochondrial and autophagic markers as well as the inhibition of trafficking via autophagosome/lysosome fusion inhibitor, bafilomycin A1, suggests a novel mechanism of AQP5 trafficking, namely the unconventional protein secretion (UPS) process of lysosomal secretion [ 155 ]. In addition, AQP5 insertion into lens fiber cell membranes can be regulated by mechanical tension and pharmacologic treatment with a muscarinic agonist, pilocarpine [ 156 ].…”

Section: Aqp5mentioning

confidence: 99%

Insight into the Mammalian Aquaporin Interactome

Törnroth-Horsefield

Chivasso

Strandberg

et al. 2022

IJMS

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Aquaporins (AQPs) are a family of transmembrane water channels expressed in all living organisms. AQPs facilitate osmotically driven water flux across biological membranes and, in some cases, the movement of small molecules (such as glycerol, urea, CO2, NH3, H2O2). Protein–protein interactions play essential roles in protein regulation and function. This review provides a comprehensive overview of the current knowledge of the AQP interactomes and addresses the molecular basis and functional significance of these protein–protein interactions in health and diseases. Targeting AQP interactomes may offer new therapeutic avenues as targeting individual AQPs remains challenging despite intense efforts.

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Lens Aquaporin-5 Inserts Into Bovine Fiber Cell Plasma Membranes Via Unconventional Protein Secretion

Cited by 8 publications

References 72 publications

Independent Membrane Binding Properties of the Caspase Generated Fragments of the Beaded Filament Structural Protein 1 (BFSP1) Involves an Amphipathic Helix

Independent Membrane Binding Properties of the Caspase Generated Fragments of the Beaded Filament Structural Protein 1 (BFSP1) Involves an Amphipathic Helix

Spatially Resolved Proteomics Reveals Lens Suture-Related Cell–Cell Junctional Protein Distributions

Insight into the Mammalian Aquaporin Interactome

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