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Szenci G, Glatz G, Takáts S, Juhász G. The Ykt6-Snap29-Syx13 SNARE complex promotes crinophagy via secretory granule fusion with Lamp1 carrier vesicles. Sci Rep 2024; 14:3200. [PMID: 38331993 PMCID: PMC10853563 DOI: 10.1038/s41598-024-53607-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2023] [Accepted: 02/02/2024] [Indexed: 02/10/2024] Open
Abstract
In the Drosophila larval salivary gland, developmentally programmed fusions between lysosomes and secretory granules (SGs) and their subsequent acidification promote the maturation of SGs that are secreted shortly before puparium formation. Subsequently, ongoing fusions between non-secreted SGs and lysosomes give rise to degradative crinosomes, where the superfluous secretory material is degraded. Lysosomal fusions control both the quality and quantity of SGs, however, its molecular mechanism is incompletely characterized. Here we identify the R-SNARE Ykt6 as a novel regulator of crinosome formation, but not the acidification of maturing SGs. We show that Ykt6 localizes to Lamp1+ carrier vesicles, and forms a SNARE complex with Syntaxin 13 and Snap29 to mediate fusion with SGs. These Lamp1 carriers represent a distinct vesicle population that are functionally different from canonical Arl8+, Cathepsin L+ lysosomes, which also fuse with maturing SGs but are controlled by another SNARE complex composed of Syntaxin 13, Snap29 and Vamp7. Ykt6- and Vamp7-mediated vesicle fusions also determine the fate of SGs, as loss of either of these SNAREs prevents crinosomes from acquiring endosomal PI3P. Our results highlight that fusion events between SGs and different lysosome-related vesicle populations are critical for fine regulation of the maturation and crinophagic degradation of SGs.
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Affiliation(s)
- Győző Szenci
- Department of Anatomy, Cell and Developmental Biology, Eötvös Loránd University, Budapest, 1117, Hungary
- Doctoral School of Biology, Institute of Biology, Eötvös Loránd University, Budapest, 1117, Hungary
| | - Gábor Glatz
- Department of Anatomy, Cell and Developmental Biology, Eötvös Loránd University, Budapest, 1117, Hungary
| | - Szabolcs Takáts
- Department of Anatomy, Cell and Developmental Biology, Eötvös Loránd University, Budapest, 1117, Hungary.
| | - Gábor Juhász
- Department of Anatomy, Cell and Developmental Biology, Eötvös Loránd University, Budapest, 1117, Hungary.
- Institute of Genetics, HUN-REN Biological Research Centre Szeged, Szeged, 6726, Hungary.
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Zhang L, Muirhead KJ, Syed ZA, Dimitriadis EK, Ten Hagen KG. A novel cysteine-rich adaptor protein is required for mucin packaging and secretory granule stability in vivo. Proc Natl Acad Sci U S A 2024; 121:e2314309121. [PMID: 38285943 PMCID: PMC10861859 DOI: 10.1073/pnas.2314309121] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2023] [Accepted: 01/02/2024] [Indexed: 01/31/2024] Open
Abstract
Mucins are large, highly glycosylated extracellular matrix proteins that line and protect epithelia of the respiratory, digestive, and urogenital tracts. Previous work has shown that mucins form large, interconnected polymeric networks that mediate their biological functions once secreted. However, how these large matrix molecules are compacted and packaged into much smaller secretory granules within cells prior to secretion is largely unknown. Here, we demonstrate that a small cysteine-rich adaptor protein is essential for proper packaging of a secretory mucin in vivo. This adaptor acts via cysteine bonding between itself and the cysteine-rich domain of the mucin. Loss of this adaptor protein disrupts mucin packaging in secretory granules, alters the mobile fraction within granules, and results in granules that are larger, more circular, and more fragile. Understanding the factors and mechanisms by which mucins and other highly glycosylated matrix proteins are properly packaged and secreted may provide insight into diseases characterized by aberrant mucin secretion.
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Affiliation(s)
- Liping Zhang
- Developmental Glycobiology Section, National Institute of Dental and Craniofacial Research, NIH, Bethesda, MD20892-4370
| | - Kayla J. Muirhead
- Developmental Glycobiology Section, National Institute of Dental and Craniofacial Research, NIH, Bethesda, MD20892-4370
- Ambry Genetics, Aliso Viejo, CA92656
| | - Zulfeqhar A. Syed
- Developmental Glycobiology Section, National Institute of Dental and Craniofacial Research, NIH, Bethesda, MD20892-4370
- Electron Microscopy Core Facility, National Heart, Lung and Blood Institute, NIH, Bethesda, MD20892
| | - Emilios K. Dimitriadis
- Trans-NIH Resource on Biomedical Engineering and Physical Science, National Institute of Biomedical Imaging and Bioengineering, NIH, Bethesda, MD20892
| | - Kelly G. Ten Hagen
- Developmental Glycobiology Section, National Institute of Dental and Craniofacial Research, NIH, Bethesda, MD20892-4370
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Boda A, Varga LP, Nagy A, Szenci G, Csizmadia T, Lőrincz P, Juhász G. Rab26 controls secretory granule maturation and breakdown in Drosophila. Cell Mol Life Sci 2023; 80:24. [PMID: 36600084 PMCID: PMC9813115 DOI: 10.1007/s00018-022-04674-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2022] [Revised: 11/29/2022] [Accepted: 12/13/2022] [Indexed: 01/06/2023]
Abstract
At the onset of Drosophila metamorphosis, plenty of secretory glue granules are released from salivary gland cells and the glue is deposited on the ventral side of the forming (pre)pupa to attach it to a dry surface. Prior to this, a poorly understood maturation process takes place during which secretory granules gradually grow via homotypic fusions, and their contents are reorganized. Here we show that the small GTPase Rab26 localizes to immature (smaller, non-acidic) glue granules and its presence prevents vesicle acidification. Rab26 mutation accelerates the maturation, acidification and release of these secretory vesicles as well as the lysosomal breakdown (crinophagy) of residual, non-released glue granules. Strikingly, loss of Mon1, an activator of the late endosomal and lysosomal fusion factor Rab7, results in Rab26 remaining associated even with the large glue granules and a concomitant defect in glue release, similar to the effects of Rab26 overexpression. Our data thus identify Rab26 as a key regulator of secretory vesicle maturation that promotes early steps (vesicle growth) and inhibits later steps (lysosomal transport, acidification, content reorganization, release, and breakdown), which is counteracted by Mon1.
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Affiliation(s)
- Attila Boda
- Department of Anatomy, Cell and Developmental Biology, Eötvös Loránd University, Budapest, Hungary
| | - Luca Petra Varga
- Department of Anatomy, Cell and Developmental Biology, Eötvös Loránd University, Budapest, Hungary
| | - Anikó Nagy
- Department of Anatomy, Cell and Developmental Biology, Eötvös Loránd University, Budapest, Hungary
| | - Győző Szenci
- Department of Anatomy, Cell and Developmental Biology, Eötvös Loránd University, Budapest, Hungary
| | - Tamás Csizmadia
- Department of Anatomy, Cell and Developmental Biology, Eötvös Loránd University, Budapest, Hungary
| | - Péter Lőrincz
- Department of Anatomy, Cell and Developmental Biology, Eötvös Loránd University, Budapest, Hungary
| | - Gábor Juhász
- Department of Anatomy, Cell and Developmental Biology, Eötvös Loránd University, Budapest, Hungary.
- Institute of Genetics, Biological Research Centre, Szeged, Hungary.
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Nagy A, Szenci G, Boda A, Al-Lami M, Csizmadia T, Lőrincz P, Juhász G, Lőw P. Ecdysone receptor isoform specific regulation of secretory granule acidification in the larval Drosophila salivary gland. Eur J Cell Biol 2022; 101:151279. [PMID: 36306596 DOI: 10.1016/j.ejcb.2022.151279] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2022] [Revised: 10/21/2022] [Accepted: 10/21/2022] [Indexed: 12/14/2022] Open
Abstract
Bulk production and release of glue containing secretory granules takes place in the larval salivary gland during Drosophila development in order to attach the metamorphosing animal to a dry surface. These granules undergo a maturation process to prepare glue for exocytosis, which includes homotypic fusions to increase the size of granules, vesicle acidification and ion uptake. The steroid hormone 20-hydroxyecdysone is known to be required for the first and last steps of this process: glue synthesis and secretion, respectively. Here we show that the B1 isoform of Ecdysone receptor (EcR), together with its binding partner Ultraspiracle, are also necessary for the maturation of glue granules by promoting their acidification via regulation of Vha55 expression, which encodes an essential subunit of the V-ATPase proton pump. This is antagonized by the EcR-A isoform, overexpression of which decreases EcR-B1 and Vha55 expression and glue granule acidification. Our data shed light on a previously unknown, ecdysone receptor isoform-specific regulation of glue granule maturation.
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Affiliation(s)
- Anikó Nagy
- Department of Anatomy, Cell and Developmental Biology, Eötvös Loránd University, Budapest, Hungary
| | - Győző Szenci
- Department of Anatomy, Cell and Developmental Biology, Eötvös Loránd University, Budapest, Hungary
| | - Attila Boda
- Department of Anatomy, Cell and Developmental Biology, Eötvös Loránd University, Budapest, Hungary
| | - Muna Al-Lami
- Department of Anatomy, Cell and Developmental Biology, Eötvös Loránd University, Budapest, Hungary
| | - Tamás Csizmadia
- Department of Anatomy, Cell and Developmental Biology, Eötvös Loránd University, Budapest, Hungary
| | - Péter Lőrincz
- Department of Anatomy, Cell and Developmental Biology, Eötvös Loránd University, Budapest, Hungary
| | - Gábor Juhász
- Department of Anatomy, Cell and Developmental Biology, Eötvös Loránd University, Budapest, Hungary; Institute of Genetics, Biological Research Centre, Szeged, Hungary.
| | - Péter Lőw
- Department of Anatomy, Cell and Developmental Biology, Eötvös Loránd University, Budapest, Hungary
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