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Turner ME, Che J, Mirhaidari GJM, Kennedy CC, Blum KM, Rajesh S, Zbinden JC, Breuer CK, Best CA, Barker JC. The lysosomal trafficking regulator "LYST": an 80-year traffic jam. Front Immunol 2024; 15:1404846. [PMID: 38774881 PMCID: PMC11106369 DOI: 10.3389/fimmu.2024.1404846] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2024] [Accepted: 04/17/2024] [Indexed: 05/24/2024] Open
Abstract
Lysosomes and lysosome related organelles (LROs) are dynamic organelles at the intersection of various pathways involved in maintaining cellular hemostasis and regulating cellular functions. Vesicle trafficking of lysosomes and LROs are critical to maintain their functions. The lysosomal trafficking regulator (LYST) is an elusive protein important for the regulation of membrane dynamics and intracellular trafficking of lysosomes and LROs. Mutations to the LYST gene result in Chédiak-Higashi syndrome, an autosomal recessive immunodeficiency characterized by defective granule exocytosis, cytotoxicity, etc. Despite eight decades passing since its initial discovery, a comprehensive understanding of LYST's function in cellular biology remains unresolved. Accumulating evidence suggests that dysregulation of LYST function also manifests in other disease states. Here, we review the available literature to consolidate available scientific endeavors in relation to LYST and discuss its relevance for immunomodulatory therapies, regenerative medicine and cancer applications.
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Affiliation(s)
- Mackenzie E. Turner
- Center for Regenerative Medicine, Abigail Wexner Research Institute at Nationwide Children’s Hospital, Columbus, OH, United States
- Molecular and Cellular Developmental Biology Graduate Program, The Ohio State University, Columbus, OH, United States
| | - Jingru Che
- Center for Regenerative Medicine, Abigail Wexner Research Institute at Nationwide Children’s Hospital, Columbus, OH, United States
| | - Gabriel J. M. Mirhaidari
- Center for Regenerative Medicine, Abigail Wexner Research Institute at Nationwide Children’s Hospital, Columbus, OH, United States
- The Ohio State University College of Medicine, Columbus, OH, United States
| | - Catherine C. Kennedy
- Center for Regenerative Medicine, Abigail Wexner Research Institute at Nationwide Children’s Hospital, Columbus, OH, United States
| | - Kevin M. Blum
- Center for Regenerative Medicine, Abigail Wexner Research Institute at Nationwide Children’s Hospital, Columbus, OH, United States
- The Ohio State University College of Medicine, Columbus, OH, United States
| | - Sahana Rajesh
- Center for Regenerative Medicine, Abigail Wexner Research Institute at Nationwide Children’s Hospital, Columbus, OH, United States
| | - Jacob C. Zbinden
- Center for Regenerative Medicine, Abigail Wexner Research Institute at Nationwide Children’s Hospital, Columbus, OH, United States
| | - Christopher K. Breuer
- Center for Regenerative Medicine, Abigail Wexner Research Institute at Nationwide Children’s Hospital, Columbus, OH, United States
| | - Cameron A. Best
- Center for Regenerative Medicine, Abigail Wexner Research Institute at Nationwide Children’s Hospital, Columbus, OH, United States
- Molecular and Cellular Developmental Biology Graduate Program, The Ohio State University, Columbus, OH, United States
| | - Jenny C. Barker
- Center for Regenerative Medicine, Abigail Wexner Research Institute at Nationwide Children’s Hospital, Columbus, OH, United States
- Department of Plastic and Reconstructive Surgery, The Ohio State University Medical Center, Columbus, OH, United States
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Lattao R, Rangone H, Llamazares S, Glover DM. Mauve/LYST limits fusion of lysosome-related organelles and promotes centrosomal recruitment of microtubule nucleating proteins. Dev Cell 2021; 56:1000-1013.e6. [PMID: 33725482 PMCID: PMC8024676 DOI: 10.1016/j.devcel.2021.02.019] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2020] [Revised: 11/17/2020] [Accepted: 02/17/2021] [Indexed: 11/28/2022]
Abstract
Lysosome-related organelles (LROs) are endosomal compartments carrying tissue-specific proteins, which become enlarged in Chediak-Higashi syndrome (CHS) due to mutations in LYST. Here, we show that Drosophila Mauve, a counterpart of LYST, suppresses vesicle fusion events with lipid droplets (LDs) during the formation of yolk granules (YGs), the LROs of the syncytial embryo, and opposes Rab5, which promotes fusion. Mauve localizes on YGs and at spindle poles, and it co-immunoprecipitates with the LDs' component and microtubule-associated protein Minispindles/Ch-TOG. Minispindles levels are increased at the enlarged YGs and diminished around centrosomes in mauve-derived mutant embryos. This leads to decreased microtubule nucleation from centrosomes, a defect that can be rescued by dominant-negative Rab5. Together, this reveals an unanticipated link between endosomal vesicles and centrosomes. These findings establish Mauve/LYST's role in regulating LRO formation and centrosome behavior, a role that could account for the enlarged LROs and centrosome positioning defects at the immune synapse of CHS patients.
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Affiliation(s)
- Ramona Lattao
- University of Cambridge, Department of Genetics, Downing Street, Cambridge CB23EH, UK.
| | - Hélène Rangone
- University of Cambridge, Department of Genetics, Downing Street, Cambridge CB23EH, UK
| | - Salud Llamazares
- Institute for Research in Biomedicine (IRB Barcelona), The Barcelona Institute of Science and Technology, Parc Cientific de Barcelona, C/ Baldiri Reixac 10, 08028 Barcelona, Spain
| | - David M Glover
- University of Cambridge, Department of Genetics, Downing Street, Cambridge CB23EH, UK; Division of Biology and Biological Engineering, California Institute of Technology, 1200 E, California Blvd, Pasadena, CA 91125, USA.
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3
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Falkenstein K, De Lozanne A. Dictyostelium LvsB has a regulatory role in endosomal vesicle fusion. J Cell Sci 2014; 127:4356-67. [PMID: 25086066 DOI: 10.1242/jcs.138123] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Defects in human lysosomal-trafficking regulator (Lyst) are associated with the lysosomal disorder Chediak-Higashi syndrome. The absence of Lyst results in the formation of enlarged lysosome-related compartments, but the mechanism for how these compartments arise is not well established. Two opposing models have been proposed to explain Lyst function. The fission model describes Lyst as a positive regulator of fission from lysosomal compartments, whereas the fusion model identifies Lyst as a negative regulator of fusion between lysosomal vesicles. Here, we used assays that can distinguish between defects in vesicle fusion versus fission. We compared the phenotype of Dictyostelium discoideum cells defective in LvsB, the ortholog of Lyst, with that of two known fission defect mutants (μ3- and WASH-null mutants). We found that the temporal localization characteristics of the post-lysosomal marker vacuolin, as well as vesicular acidity and the fusion dynamics of LvsB-null cells are distinct from those of both μ3- and WASH-null fission defect mutants. These distinctions are predicted by the fusion defect model and implicate LvsB as a negative regulator of vesicle fusion.
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Affiliation(s)
- Kristin Falkenstein
- Section of Molecular Cell and Developmental Biology and Institute for Cellular and Molecular Biology, University of Texas at Austin, Austin, TX 78712, USA
| | - Arturo De Lozanne
- Section of Molecular Cell and Developmental Biology and Institute for Cellular and Molecular Biology, University of Texas at Austin, Austin, TX 78712, USA
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4
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Orlow SJ, Chakraborty AK, Pawelek JM. Membrane glycoproteins common to vesicles and melanosomes in mouse melanoma cells. PIGMENT CELL RESEARCH 2008; Suppl 2:162-70. [PMID: 1384030 DOI: 10.1111/j.1600-0749.1990.tb00368.x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Affiliation(s)
- S J Orlow
- Department of Dermatology, New York University Medical Center, NY 10016
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5
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Introne W, Boissy RE, Gahl WA. Clinical, molecular, and cell biological aspects of Chediak-Higashi syndrome. Mol Genet Metab 1999; 68:283-303. [PMID: 10527680 DOI: 10.1006/mgme.1999.2927] [Citation(s) in RCA: 201] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Chediak-Higashi syndrome (CHS) is a rare autosomal recessive disorder characterized by variable degrees of oculocutaneous albinism, easy bruisability, and bleeding as a result of deficient platelet dense bodies, and recurrent infections, with neutropenia, impaired chemotaxis and bactericidal activity, and abnormal NK cell function. Neurologic involvement is variable, but often includes peripheral neuropathy. Most patients also undergo an "accelerated phase," which is a nonmalignant lymphohistiocytic infiltration of multiple organs resembling lymphoma. Death often occurs in the first decade from infection, bleeding, or development of the accelerated phase. The hallmark of CHS is the presence of huge cytoplasmic granules in circulating granulocytes and many other cell types. These granules are peroxidase-positive and contain lysosomal enzymes, suggesting that they are giant lysosomes or, in the case of melanocytes, giant melanosomes. The underlying defect in CHS remains elusive, but the disorder can be considered a model for defects in vesicle formation, fusion, or trafficking. Because the beige mouse demonstrates many characteristics similar to those of human CHS patients, including dilution of coat color, recurrent infections, and the presence of giant granules, it is considered the animal homologue of CHS. The beige gene, Lyst, was mapped and sequenced in 1996, prompting identification of the human LYST gene on chromosome 1q42. Lyst and LYST show 86.5% sequence homology. LYST encodes a 429 kDa protein with a function that remains unknown, but the source of extensive speculation among students of cell biology.
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Affiliation(s)
- W Introne
- Heritable Disorders Branch, National Institutes of Health, Bethesda, Maryland
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6
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Sagai T, Koide T, Endo M, Tanoue K, Kikkawa Y, Yonekawa H, Ishiguro S, Tamai M, Matsuda Y, Wakana S, Shiroishi T. rim2 (recombination-induced mutation 2) is a new allele of pearl and a mouse model of human Hermansky-Pudlak syndrome (HPS): genetic and physical mapping. Mamm Genome 1998; 9:2-7. [PMID: 9434937 DOI: 10.1007/s003359900670] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
A mouse mutation, rim2, is one of a series of spontaneous mutations that arose from the intra-MHC recombinants between Japanese wild mouse-derived wm7 and laboratory MHC haplotypes. This mutation is single recessive and characterized by diluted coat color and hypo-pigmentation of the eyes. We mapped the rim2 gene close to an old coat color mutation, pearl (pe), on Chromosome (Chr) 13 by the high-density linkage analysis. The pearl mutant is known to have abnormalities similar to Hermansky-Pudlak syndrome (HPS), a human hemorrhagic disorder, characterized by albinism and storage pool deficiency (SPD) of dense granules in platelets. A mating cross of C57BL10/Slc-rim2/rim2 and C57BL/6J-pe/pe showed no complementation of coat color. Additionally, characteristics similar to SPD were also observed in rim2. Thus, rim2 appeared to be a new allele of the pe locus and serves as a mouse model for human HPS. We have made a YAC contig covering the rim2/pe locus toward positional cloning of the causative gene.
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Affiliation(s)
- T Sagai
- Mammalian Genetics Laboratory, National Institute of Genetics, Mishima, Japan
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7
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Provance DW, Wei M, Ipe V, Mercer JA. Cultured melanocytes from dilute mutant mice exhibit dendritic morphology and altered melanosome distribution. Proc Natl Acad Sci U S A 1996; 93:14554-8. [PMID: 8962090 PMCID: PMC26171 DOI: 10.1073/pnas.93.25.14554] [Citation(s) in RCA: 148] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/1996] [Accepted: 09/23/1996] [Indexed: 02/03/2023] Open
Abstract
Mutant alleles at the dilute unconventional myosin heavy chain locus cause diluted coat color, opisthotonic seizures, and death. The dilute coat color phenotype is caused by irregular clumping of pigment in the hair, but amounts of melanin are unchanged from wild-type controls. The melanocyte phenotype has been described as adendritic, since hair bulb and Harderian gland melanocytes appear to be rounded in tissue sections. These observations do not exclude the possibility that the processes lack pigment, since the melanocyte shape was judged by the distribution of melanin. We have tested this hypothesis by culturing primary melanocytes from dilute mutant and wild-type mice. The mutant melanocytes do not lack processes; instead, they exhibit a concentrated perinuclear distribution of melanosomes, while wild-type melanocytes have a very uniform cytoplasmic distribution of melanosomes. Electron micrographs show no detectable differences in melanosome morphology or maturation between dilute and wild-type melanocytes. Immunofluorescence experiments indicate that the dilute protein is concentrated in regions of the cytoplasm that contain melanosomes. These experiments show that the dilute myosin is necessary for the localization of melanosomes, either by active transport or tethering.
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Affiliation(s)
- D W Provance
- McLaughlin Research Institute, Great Falls, MT 59405, USA
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Nagle DL, Karim MA, Woolf EA, Holmgren L, Bork P, Misumi DJ, McGrail SH, Dussault BJ, Perou CM, Boissy RE, Duyk GM, Spritz RA, Moore KJ. Identification and mutation analysis of the complete gene for Chediak-Higashi syndrome. Nat Genet 1996; 14:307-11. [PMID: 8896560 DOI: 10.1038/ng1196-307] [Citation(s) in RCA: 343] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Chediak-Higashi syndrome (CHS) is a rare, autosomal recessive disorder characterized by hypopigmentation, severe immunologic deficiency with neutropenia and lack of natural killer (NK) cells, a bleeding tendency and neurologic abnormalities. Most patients die in childhood. The CHS hallmark is the occurrence of giant inclusion bodies and organelles in a variety of cell types, and protein sorting defects into these organelles. Similar abnormalities occur in the beige mouse, the proposed model for human CHS. Two groups have recently reported the identification of the beige gene, however the two cDNAs were not at all similar. Here we describe the sequence of a human cDNA homologous to mouse beige, identify pathologic mutations and clarify the discrepancies of the previous reports. Analysis of the CHS polypeptide demonstrates that its modular architecture is similar to the yeast vacuolar sorting protein, VPS15.
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Affiliation(s)
- D L Nagle
- Millennium Pharmaceuticals, Inc., Cambridge, Massachusetts 02139, USA
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9
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Gow JB, Lyerla TA, Lainwala S. Enlarged dysmorphic lysosomes in an established beige (C57BL/6J;bgJ(/bgJ)) mouse mutant fibroblast line: a reversible characteristic. In Vitro Cell Dev Biol Anim 1996; 32:457-61. [PMID: 8889598 DOI: 10.1007/bf02723046] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
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10
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Barbosa MD, Nguyen QA, Tchernev VT, Ashley JA, Detter JC, Blaydes SM, Brandt SJ, Chotai D, Hodgman C, Solari RC, Lovett M, Kingsmore SF. Identification of the homologous beige and Chediak-Higashi syndrome genes. Nature 1996; 382:262-5. [PMID: 8717042 PMCID: PMC2893578 DOI: 10.1038/382262a0] [Citation(s) in RCA: 359] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Vesicular transport to and from the lysosome and late endosome is defective in patients with Chediak-Higashi syndrome (CHS) and in mutant beige (bg) mice. CHS and bg cells have giant, perinuclear vesicles with characteristics of late endosomes and lysosomes that arise from dysregulated homotypic fusion. CHS and bg lysosomes also exhibit compartmental missorting of proteins, such as elastase, glucuronidase and cathepsin G. Lyst, a candidate gene for bg, was identified by direct complementary DNA selection from a yeast artificial chromosome (YAC) clone containing a 650-kilobase segment of the bg-critical region on mouse chromosome 13. Lyst is disrupted by a 5-kilobase deletion in bg mice, and Lyst messenger RNA is markedly reduced in bg homozygotes. The homologous human gene, LYST, is highly conserved with mouse Lyst, and contains a frame-shift mutation at nucleotides 117-118 of the coding domain in a CHS patient. Thus bg mice and human CHS patients have homologous disorders associated with Lyst mutations. Lyst encodes a protein with a carboxy-terminal prenylation motif and multiple potential phosphorylation sites. Lyst protein is predicted to form extended helical domains, and has a region of sequence similar to stathmin, a coiled-coil phosphoprotein thought to act as a relay integrating cellular signal response coupling.
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Affiliation(s)
- M D Barbosa
- Department of Medicine, University of Florida, Gainesville 32610, USA
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11
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Ozaki K, Maeda H, Nishikawa T, Nishimura M, Narama I. Chediak-Higashi syndrome in rats: light and electron microscopical characterization of abnormal granules in beige rats. J Comp Pathol 1994; 110:369-79. [PMID: 8056871 DOI: 10.1016/s0021-9975(08)80314-3] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Chediak-Higashi syndrome (CHS) is a rare disease occurring in several animal species. Recently, mutant beige rats with CHS were found among DA strain rats in Japan. In the present study, histological examination of beige rats revealed giant granules in the hepatocytes, renal proximal tubules, submandibular ducts, thyroid follicular cells, granulocytes, mast cells, melanocytes, retinal pigment epithelial cells and globular leucocytes. Ultrastructurally, these granules varied from enlarged lysosomes, which were amorphous, granular or filamentous, to giant mast cell granules, crystalloid granules of eosinophils and slightly enlarged neutrophil granules. These findings bore many similarities to those in the beige mouse, which is a well known animal model for CHS, but some differences were apparent. Thus the giant granules of beige rats were larger and more easy to observe than those in beige mice. The study indicated that the beige rat may prove useful as an animal model for CHS.
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Affiliation(s)
- K Ozaki
- Research Institute of Drug Safety, Setsunan University, Osaka, Japan
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Gow JB, Lainwala S, Lyerla TA. Cellular expression of the beige mouse mutation and its correction in hybrids with control human fibroblasts. In Vitro Cell Dev Biol Anim 1993; 29A:884-91. [PMID: 8167906 DOI: 10.1007/bf02631368] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Fibroblasts from a beige mouse (C57BL/6J; bgJ bgJ) have been established and maintained in culture for more than 3 yr. At early passages, the mutant cells were distinguishable from C57BL/6J control mouse fibroblasts at the ultrastructural level by the presence of enlarged cytoplasmic granules. After continuous passaging, this distinguishing feature was lost from the mutant cells, correlated with their increased growth rate. Clustered, perinuclear distribution of lysosomes was retained, however, and was quantitatively different at any passage number of the beige cell line from the dispersed distribution of these organelles in control mouse fibroblasts, as analyzed by computer-aided, video-enhanced light microscopy. In somatic cell hybrids between the established beige cell line and a control human diploid fibroblast cell strain, seven uncorrected hybrid lines retained a lysosomal dispersion pattern statistically indistinguishable from that of the beige mouse cell lines. Three corrected hybrid lines had lysosomal dispersion patterns that were significantly different from the beige parent line and indistinguishable from that of the control mouse fibroblast line. Thus, lysosomal dispersion can be used objectively and quantitatively to distinguish mutant beige and control mouse fibroblasts and corrected vs. uncorrected cell hybrids made from the beige/control human somatic cell crosses.
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Affiliation(s)
- J B Gow
- Department of Biology, Clark University, Worcester, Massachusetts 01610
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Mattson P, Lorenz S, Kowal J. The effects of ACTH on acid phosphatase activity in endosomes, GERL and lysosomes of cultured adrenal tumor cells. VIRCHOWS ARCHIV. B, CELL PATHOLOGY INCLUDING MOLECULAR PATHOLOGY 1986; 51:137-53. [PMID: 2873677 DOI: 10.1007/bf02899024] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Cultured cells derived from a mouse adrenocortical tumor transplant are unspecialized in appearance, but produce basal levels of steroids and demonstrate a near-immediate steroidogenic response to ACTH. There is biochemical evidence that ACTH induces increases in the uptake of serum lipoproteins by these cells and that this material is hydrolyzed in lysosomes to free cholesterol, a precursor for steroid end products. To investigate morphologically the role of lysosomes in the steroidogenic activity of these cells, cultures were incubated for 4 h with and without ACTH, then processed for the ultrastructural localization of acid phosphatase (ACPase), a marker enzyme for lysosomes, and for GERL, the lysosome-forming subcompartment of the Golgi, and examined by TEM and HVEM. Steroid output was determined by a fluorometric technique. Unstimulated cells secreted basal levels of steroids. By TEM, large endosomes, some containing semi-compact material and ACPase reaction product, were occasionally seen at the cell periphery and in the Golgi region. The Golgi and GERL were poorly developed. Residual bodies, a few of them ACPase+, appeared in the Golgi region and in microtubule-associated clusters near the cell membrane. ACTH-stimulated cells secreted steroids at 8-10 fold basal values. In TEM records, they displayed numerous ACPase+ endosomes between the cell periphery and the Golgi. The Golgi and GERL regions appeared to be hypertrophied and many large, inclusion-containing, strongly ACPase+ residual bodies appeared here and in elongated microtubule-containing cell processes. HVEM micrographs showed more definitively that ACTH produced distinct increases in the size of GERL and in the number of ACPase+ organelles. Our results suggest that in unstimulated cells, endosomes, presumably containing media-derived material, gain lysosomal enzymes in or near GERL, are transformed to residual bodies as their contents are hydrolyzed, and are subsequently translocated by microtubules to the cell periphery for exocytosis. ACTH appears to intensify all of these effects. The "giant" lysosomes seen in stimulated cells may result from a fusion of smaller lysosomes. Their amorphous contents may reflect an inefficient hydrolysis of LDL to free cholesterol.
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Willingham MC, Pastan IH. Image intensification techniques for detection of proteins in cultured cells. Methods Enzymol 1983; 98:266-83, 635. [PMID: 6669050 DOI: 10.1016/0076-6879(83)98154-5] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
We describe here the components and uses of two image intensifier systems. The SIT camera system is convenient, relatively inexpensive, readily adaptable to most microscopes, and reliable. It suffers from lack of resolution at high gain levels and the inability to extend its sensitivity by accumulating an image over time. The EMI system is expensive and bulky and requires special adaptation to the microscope and special image recording devices in its output. It has extraordinary sensitivity and resolution, however, and allows experiments to be carried out that are otherwise not possible. Other systems similar to those described here are also commercially available and, in general, have similar advantages and disadvantages. The choice of the proper type of system varies with the particular application. These systems amplify the amount of light in an available image within constraints of gain and resolution and produce a publishable record of what otherwise might not be able to be recorded. These systems cannot improve images that contain too much background nor improve the resolution inherent in the microscopic method employed.
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