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Abstract
Cell surface area is maintained in most cells by coupling exocytotic activity to compensatory endocytosis, a process that specifically retrieves membrane inserted by exocytosis. Although such coupling mechanisms seem to be ubiquitous, the mechanisms through which these membrane trafficking events are linked have remained elusive. A mechanism for coupling exocytosis to endocytosis in fruit fly nerve terminals that depends on the exocytotic insertion of vesicular calcium channels into the plasma membrane has recently been identified. This coupling mechanism resembles one previously described in sea urchin eggs. Here, I compare the similarities and differences of the processes involved in linking exocytosis to endocytosis in these two invertebrate systems and speculate on whether the vertebrate coupling mechanism might also depend on vesicular channels.
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Affiliation(s)
- Steven S Vogel
- National Institute on Alcohol Abuse and Alcoholism, National Institutes of Health, Rockville, MD 20892, USA.
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Mitchell KJ, Pinton P, Varadi A, Tacchetti C, Ainscow EK, Pozzan T, Rizzuto R, Rutter GA. Dense core secretory vesicles revealed as a dynamic Ca(2+) store in neuroendocrine cells with a vesicle-associated membrane protein aequorin chimaera. J Cell Biol 2001; 155:41-51. [PMID: 11571310 PMCID: PMC2150797 DOI: 10.1083/jcb.200103145] [Citation(s) in RCA: 165] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The role of dense core secretory vesicles in the control of cytosolic-free Ca(2+) concentrations ([Ca(2+)](c)) in neuronal and neuroendocrine cells is enigmatic. By constructing a vesicle-associated membrane protein 2-synaptobrevin.aequorin chimera, we show that in clonal pancreatic islet beta-cells: (a) increases in [Ca(2+)](c) cause a prompt increase in intravesicular-free Ca(2+) concentration ([Ca(2+)]SV), which is mediated by a P-type Ca(2+)-ATPase distinct from the sarco(endo) plasmic reticulum Ca(2+)-ATPase, but which may be related to the PMR1/ATP2C1 family of Ca(2+) pumps; (b) steady state Ca(2+) concentrations are 3-5-fold lower in secretory vesicles than in the endoplasmic reticulum (ER) or Golgi apparatus, suggesting the existence of tightly bound and more rapidly exchanging pools of Ca(2+); (c) inositol (1,4,5) trisphosphate has no impact on [Ca(2+)](SV) in intact or permeabilized cells; and (d) ryanodine receptor (RyR) activation with caffeine or 4-chloro-3-ethylphenol in intact cells, or cyclic ADPribose in permeabilized cells, causes a dramatic fall in [Ca(2+)](SV). Thus, secretory vesicles represent a dynamic Ca(2+) store in neuroendocrine cells, whose characteristics are in part distinct from the ER/Golgi apparatus. The presence of RyRs on secretory vesicles suggests that local Ca(2+)-induced Ca(2+) release from vesicles docked at the plasma membrane could participate in triggering exocytosis.
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Affiliation(s)
- K J Mitchell
- Department of Biochemistry, University of Bristol, BS8 1TD Bristol, United Kingdom
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Affiliation(s)
- G A Rutter
- Department of Biochemistry, School of Medical Sciences, University of Bristol, United Kingdom.
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Pezzati R, Bossi M, Podini P, Meldolesi J, Grohovaz F. High-resolution calcium mapping of the endoplasmic reticulum-Golgi-exocytic membrane system. Electron energy loss imaging analysis of quick frozen-freeze dried PC12 cells. Mol Biol Cell 1997; 8:1501-12. [PMID: 9285821 PMCID: PMC276172 DOI: 10.1091/mbc.8.8.1501] [Citation(s) in RCA: 98] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
The calcium pools segregated within the endoplasmic reticulum, Golgi complex, exocytic, and other organelles are believed to participate in the regulation of a variety of cell functions. Until now, however, the precise intracellular distribution of the element had not been established. Here, we report about the first high-resolution calcium mapping obtained in neurosecretory PC12 cells by the imaging mode of the electron energy loss spectroscopy technique. The preparation procedure used included quick freezing of cell monolayers, followed by freeze-drying, fixation with OSO4 vapors, resin embedding, and cutting of very thin sections. Conventional electron microscopy and high-resolution immunocytochemistry revealed a high degree of structural preservation, a condition in which inorganic elements are expected to maintain their native distribution. Within these cells, calcium signals of nucleus, cytosol, and most mitochondria remained below detection, whereas in other organelles specific patterns were identified. In the endoplasmic reticulum, the distribution was heterogeneous with strongly positive cisternae (more often the nuclear envelope and stacks of parallel elements that are frequent in quick frozen preparations) lying in the proximity of or even in direct continuity with other, apparently negative cisternae. The Golgi complexes were labeled strongly and uniformly in all cisternae and part of their vesicles, with no appreciable differences along the cis-trans axis. Weaker or negative signals were recorded from the trans-Golgi network elements and from scattered vesicles, whereas in contrast secretion granules were strongly positive for calcium. These results are discussed in relation to the existing knowledge about the mechanisms of calcium transport in the variations organelles, and about the processes and functions regulated by organelle lumenal calcium in eukaryotic cells.
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Affiliation(s)
- R Pezzati
- Consiglio Nazionale delle Ricerche, Cellular and Molecular Pharmacology Center, Milan, Italy
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5
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Three-dimensional organization of smooth endoplasmic reticulum in hippocampal CA1 dendrites and dendritic spines of the immature and mature rat. J Neurosci 1997. [PMID: 8987748 DOI: 10.1523/jneurosci.17-01-00190.1997] [Citation(s) in RCA: 437] [Impact Index Per Article: 16.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Recent studies have shown high levels of calcium in activated dendritic spines, where the smooth endoplasmic reticulum (SER) is likely to be important for regulating calcium. Here, the dimensions and organization of the SER in hippocampal spines and dendrites were measured through serial electron microscopy and three-dimensional analysis. SER of some form was found in 58% of the immature spines and in 48% of the adult spines. Less than 50% of the small spines at either age contained SER, suggesting that other mechanisms, such as cytoplasmic buffers, regulate ion fluxes within their small volumes. In contrast, >80% of the large mushroom spines of the adult had a spine apparatus, an organelle containing stacks of SER and dense-staining plates. Reconstructed SER occupied 0.001-0.022 microm3, which was only 2-3.5% of the total spine volume; however, the convoluted SER membranes had surface areas of 0.12-2.19 microm2, which were 12 to 40% of the spine surface area. Coated vesicles and multivesicular bodies occurred in some spines, suggesting local endocytotic activity. Smooth vesicles and tubules of SER were found in continuity with the spine plasma membrane and margins of the postsynaptic density (PSD), respectively, suggesting a role for the SER in the addition and recycling of spine membranes and synapses. The amount of SER in the parent dendrites was proportional to the number of spines and synapses originating along their lengths. These measurements support the hypothesis that the SER regulates the ionic and structural milieu of some, but not all, hippocampal dendritic spines.
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Grohovaz F, Bossi M, Pezzati R, Meldolesi J, Tarelli FT. High resolution ultrastructural mapping of total calcium: electron spectroscopic imaging/electron energy loss spectroscopy analysis of a physically/chemically processed nerve-muscle preparation. Proc Natl Acad Sci U S A 1996; 93:4799-803. [PMID: 8643483 PMCID: PMC39359 DOI: 10.1073/pnas.93.10.4799] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
We report on a procedure for tissue preparation that combines thoroughly controlled physical and chemical treatments: quick-freezing and freeze-drying followed by fixation with OsO4 vapors and embedding by direct resin infiltration. Specimens of frog cutaneous pectoris muscle thus prepared were analyzed for total calcium using electron spectroscopic imaging/electron energy loss spectroscopy (ESI/EELS) approach. The preservation of the ultrastructure was excellent, with positive K/Na ratios revealed in the fibers by x-ray microanalysis. Clear, high-resolution EELS/ESI calcium signals were recorded from the lumen of terminal cisternae of the sarcoplasmic reticulum but not from longitudinal cisternae, as expected from previous studies carried out with different techniques. In many mitochondria, calcium was below detection whereas in others it was appreciable although at variable level. Within the motor nerve terminals, synaptic vesicles as well as some cisternae of the smooth endoplasmic reticulum yielded positive signals at variance with mitochondria, that were most often below detection. Taken as a whole, the present study reveals the potential of our experimental approach to map with high spatial resolution the total calcium within individual intracellular organelles identified by their established ultrastructure, but only where the element is present at high levels.
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Affiliation(s)
- F Grohovaz
- "Consiglio Nazionale delle Ricerche," Cellular and Molecular Pharmacology Center, University of Milan, Italy
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7
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Burns ME, Augustine GJ. Synaptic structure and function: dynamic organization yields architectural precision. Cell 1995; 83:187-94. [PMID: 7585936 DOI: 10.1016/0092-8674(95)90160-4] [Citation(s) in RCA: 107] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Affiliation(s)
- M E Burns
- Department of Neurobiology, Duke University Medical Center, Durham, North Carolina 27710, USA
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8
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Door R, Gängler D. Multiple least-squares fitting for quantitative electron energy-loss spectroscopy — an experimental investigation using standard specimens. Ultramicroscopy 1995. [DOI: 10.1016/0304-3991(94)00198-v] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Hardcastle S, Koranda SF, Tonner BP, Mercanti D, Ciotti MT, Perfetti P, Margaritondo G. Photoemission spectromicroscopy of neurons. PHYSICAL REVIEW. E, STATISTICAL PHYSICS, PLASMAS, FLUIDS, AND RELATED INTERDISCIPLINARY TOPICS 1993; 47:2117-2121. [PMID: 9960232 DOI: 10.1103/physreve.47.2117] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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10
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LoPachin RM, Saubermann AJ. Disruption of cellular elements and water in neurotoxicity: studies using electron probe X-ray microanalysis. Toxicol Appl Pharmacol 1990; 106:355-74. [PMID: 1701929 DOI: 10.1016/0041-008x(90)90333-p] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Regulation of elements and water in nerve cells is a complex, multifaceted process which appears to be vulnerable to neurotoxic events. However, much of our knowledge concerning the potential role of elements in nerve cell injury is limited by the relatively gross level of corresponding analyses. If we are to confirm and understand the proposed role, more precise and detailed information is needed. As indicated in this commentary, research employing electron probe microanalysis and digital X-ray imaging has begun to provide this necessary information. Recent EPMA studies of nerve and glial cells in the peripheral and central nervous systems have shown that each cell type and their corresponding morphologic compartments exhibit unique distributions of elements and water. The use of microprobe analysis has allowed us to document precisely how elements and water redistribute in morphological compartments of damaged nerve cells. Accumulating evidence from EPMA studies suggests that, rather than being an epiphenomenon, intracellular changes in diffusible elements might mediate the functional and structural consequences of neurotoxic insult. It is also evident from this research that elements other than Ca might play a pertinent role in the injury response and that changes in intraneuronal elemental composition might develop according to a specific temporal pattern, e.g., transection-induced sequential alterations in axonal K, Na, Cl, and Ca. Therefore, rather than conducting end-point studies, longitudinal investigations are necessary to define the sequential pattern of elemental perturbation associated with a given neurotoxic event. Such research can also help identify the role of individual elements in the injury response. Future microprobe studies should be combined with measurements of ion levels (e.g., using fura-2 or ion selective electrodes) to provide a comprehensive and dynamic view of elemental deregulation. In addition, parallel biochemical studies should be performed to determine mechanisms of elemental disruption and possible biochemical and metabolic consequences of this disruption. Although evidence presented in this commentary suggests that each type of neurotoxic event produces a characteristic pattern of decompartmentalization, further work is necessary to confirm this possibility. Finally, based on a presumed involvement of elements in nerve injury, efforts are currently underway in several laboratories to develop appropriate pharmacological therapies for certain chemical- and trauma-induced neuropathological conditions (Dretchen et al., 1986; El-Fawal et al., 1989; Beattie et al., 1989).(ABSTRACT TRUNCATED AT 400 WORDS)
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Affiliation(s)
- R M LoPachin
- Department of Anesthesiology, Medical School, SUNY, Stony Brook 11794-8480
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Meldolesi J, Madeddu L, Pozzan T. Intracellular Ca2+ storage organelles in non-muscle cells: heterogeneity and functional assignment. BIOCHIMICA ET BIOPHYSICA ACTA 1990; 1055:130-40. [PMID: 2242382 DOI: 10.1016/0167-4889(90)90113-r] [Citation(s) in RCA: 137] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Affiliation(s)
- J Meldolesi
- Department of Pharmacology, CNR Center of Cytopharmacology, University of Milan, Italy
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12
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Wróblewski R. In situ elemental analysis and visualization in cryofixed nervous tissues. X-ray microanalytical investigations of embryological and mature brain, inner ear, photoreceptors, muscle and muscle spindles. Comparison of preparation methods for analysis and visualization at cellular and subcellular levels. J Microsc 1989; 155:81-112. [PMID: 2671383 DOI: 10.1111/j.1365-2818.1989.tb04299.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
For meaningful X-ray microanalysis (XRMA) in biology and medicine, the development of preparative and quantitative methods has been necessary. The methods need to preserve close to in vivo distribution of diffusible ions with at the same time reasonable morphological preservation of the tissue. Analyses at low and middle microanalytical resolution are useful at the initial stages of an investigation or when data from large populations of samples have to be acquired. Cryomicrotomy, which makes it possible for the single cells within semi-thin and thick cryosections examined by X-ray microanalysis to be further characterized histochemically (enzyme and substrate content), has been adopted for several pathophysiological studies. The method is particularly suitable for the analysis of complex morphological tissues with many cell types as in the brain or sensory organs of the internal ear. For microanalysis at the subcellular level, we developed a preparative procedure based on the frozen fixed preparation which is freeze-dried in vacuo at -80 degrees C and then at the same temperature, without breaking the vacuum, impregnated with a low-temperature Lowicryl-type resin. The resin is polymerized by u.v. light. This method prevents redistribution of the ions in the tissue and retains the antigenicity of the tissue. A considerable number of cells can be analysed simultaneously and the elemental composition in different cell compartments can be compared due to the similar analytical conditions within the section. An alternative to thin plastic sections of freeze-dried material is thin cryosections cut at -150 degrees C and analysed at low temperatures. Although some methodological problems still exist in preparation of cryosections, this type of section is potentially the most useful in analysis of diffusible ions, especially calcium which in most biological systems is present in very low concentrations. New preparative techniques for XRMA brought severe problems in visualization of the specimens prepared by cryomethods. Charging, low contrast, mass loss and contamination, which are often negligible in conventional electron microscopy, have still to be solved in XRMA of cryoprepared specimens. However, the methods of semi-thin and thick cryosectioning and low-temperature embedding were successfully used for analysis of cells and organelles and for the study of fluids in restricted biological spaces such as the inner ear, muscle spindles and ventricles of the brain in rats. Accordingly, examinations which were impossible by micropuncture and ion selective techniques could be carried out by XRMA.(ABSTRACT TRUNCATED AT 400 WORDS)
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Affiliation(s)
- R Wróblewski
- Department of Pathology, Karolinska Institute, Stockholm, Sweden
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Andrews SB, Leapman RD, Landis DM, Reese TS. Activity-dependent accumulation of calcium in Purkinje cell dendritic spines. Proc Natl Acad Sci U S A 1988; 85:1682-5. [PMID: 3422755 PMCID: PMC279838 DOI: 10.1073/pnas.85.5.1682] [Citation(s) in RCA: 49] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
The calcium content of synapses of parallel fibers on Purkinje cell dendritic spines was determined by electron probe x-ray microanalysis of freeze-dried cryosections from directly frozen slices of mouse cerebellar cortex. In fresh slices frozen within 20-30 sec of excision, calcium concentrations ranging from 0.8 to 18.6 mmol/kg of dry weight were measured in cisterns of smooth endoplasmic reticulum within Purkinje cell dendritic spines. The average calcium content of spine cisterns in rapidly excised slices (6.7 +/- 0.6 mmol/kg of dry weight +/- SEM) was higher than the average calcium content of spine cisterns in brain slices incubated without stimulation for 1-2 hr before direct freezing (2.5 +/- 0.4 mmol/kg of dry weight). Depolarization of incubated cerebellar slices by isotonic 55 mM KCl resulted in the accumulation within spine cisterns of very high amounts of calcium or isotonically substituted strontium, both derived from the extracellular fluid. These results suggest that one function of spine cisterns is to sequester free calcium that enters the spine through ligand-gated or voltage-gated channels during synaptic transmission.
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Affiliation(s)
- S B Andrews
- Laboratory of Neurobiology, National Institute of Neurological and Communicative Disorders and Stroke, Bethesda, MD 20892
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LeFurgey A, Bond M, Ingram P. Frontiers in electron probe microanalysis: application to cell physiology. Ultramicroscopy 1988; 24:185-219. [PMID: 3281355 DOI: 10.1016/0304-3991(88)90311-7] [Citation(s) in RCA: 55] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
The application of electron probe microanalysis techniques, using X-ray and electron energy loss instruments, to problems in cell physiology is reviewed. The details of the special methodological requirements for the analysis of cryosections at high spatial resolution in an analytical electron microscope are discussed together with a comprehensive review of data obtained on major organ systems and cell types.
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Affiliation(s)
- A LeFurgey
- Department of Physiology, Duke University, Durham, North Carolina 27710
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Electron probe microanalysis of the subcellular compartments of bovine adrenal chromaffin cells. Comparison of chromaffin granules in situ and in vitro. J Biol Chem 1988. [DOI: 10.1016/s0021-9258(19)57329-x] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
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Fiori CE, Leapman RD, Swyt CR, Andrews SB. Quantitative X-ray mapping of biological cryosections. Ultramicroscopy 1988; 24:237-49. [PMID: 3281357 DOI: 10.1016/0304-3991(88)90313-0] [Citation(s) in RCA: 32] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
The potential for applying X-ray mapping to the elemental microanalysis of biological cryosections is discussed. Methods are described for acquiring and processing data, including use of the top-hat digital filter to remove the average effects of the background contribution. Practical considerations for X-ray mapping are discussed in terms of typical counts per pixel and minimum detectability which depends on the number of pixels chosen to integrate the signal. These aspects are illustrated with elemental maps (Na, P, K, Ca and Fe) from freeze-dried cryosections of mouse cerebellar cortex. A calcium sensitivity in the range 0.5 to 2.5 mmol/kg wet weight of tissue is demonstrated. The correction for overlap of potassium K beta and calcium K alpha is demonstrated with X-ray maps from cryosectioned synaptosomes of squid optic lobe. Quantitative results obtained using internal standards to determine wet weight concentrations are in reasonable agreement with expected values. Alternate schemes applicable to X-ray maps for determining the dry mass concentration, such as the peak/continuum (Hall method), are also discussed.
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Affiliation(s)
- C E Fiori
- Biomedical Engineering and Instrumentation Branch, National Institutes of Health, Bethesda, Maryland 20892
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18
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Abstract
Cerebellin is a hexadecapeptide that has been biochemically characterized and localized to cerebellar Purkinje cells and certain neurons of the dorsal cochlear nucleus (DCoN) of rat. Among rabbit antisera produced to synthetic cerebellins, one (C1) gave specific immunostaining of the Purkinje neuronal cell body, initial axon segment, and main stem dendrites, while another (R2) reacted with peripheral dendritic structures. This complementarity of staining was also present during cerebellar development. By electron microscopy, the immunoreaction product was localized to polyribosomal domains with antiserum C1 and to dendritic spines with antiserum R2, in both cerebellar cortex and DCoN. In the spine, the structure most strongly stained was the postsynaptic density, but some reaction product was adsorbed to the plasma membrane, the spine apparatus, and the granulofibrillar cytoplasmic component. Antiserum R2 also stained lysosome-like bodies. We suggest that antiserum C1 recognizes cerebellin precursor(s) and antiserum R2 mature peptide(s) and perhaps degradation product. There is structural homology between cerebellin and residues 625-641 of the polyimmunoglobulin transporter. The functional implications of this homology and other possible roles of cerebellin are discussed.
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Affiliation(s)
- E Mugnaini
- Laboratory of Neuromorphology, University of Connecticut, Storrs 06268
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