Topography of Ca2+-sequestering endoplasmic reticulum in photoreceptors and pigmented glial cells in the compound eye of the honeybee drone

Baumann, Otto; Walz, Bernd

doi:10.1007/bf00218786

Cited by 67 publications

(46 citation statements)

References 42 publications

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“…The present study demonstrates directly that the wellcharacterized submicrovillar cisternae of ER in invertebrate photoreceptors (11,29) are the source of Ins(1,4,5)P3-mediated (12,13) Ca2" release during photostimulation.…”

Section: Discussionsupporting

confidence: 56%

“…Consequently, little is known about the ion movements that must occur during Ca2+ release, to maintain charge balance across the ER membrane. The large sacs of ER in bee photoreceptors (11) are uniquely suitable for addressing these questions because the size makes them clearly identifiable in ultrathin freeze-dried cryosections and allows unambiguous experiments in which the analyzed area is completely within the ER cisternae. Therefore, we determined by electron probe x-ray microanalysis (EPMA) the elemental composition of the ER in situ, in the dark and during light stimulation, that, in invertebrates, is known to be followed by Ins(1,4,5)P3-mediated (12,13) intracellular Ca2' release (14,15).…”

mentioning

confidence: 99%

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Electron probe microanalysis of calcium release and magnesium uptake by endoplasmic reticulum in bee photoreceptors.

Baumann

Walz

Somlyo

et al. 1991

Proc. Natl. Acad. Sci. U.S.A.

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Honey bee photoreceptors contain large sacs of endoplasmic reticulum (ER) that can be located unequivocally in freeze-dried cryosections. The elemental composition of the ER was determined by electron probe x-ray microanalysis and was visualized in high-resolution x-ray maps. In the ER of dark-adapted photoreceptors, the Ca concentration was 47.5 ± 1.1 mmol/kg (dry weight) (mean ± SEM). During a 3-sec nonsaturating light stimulus, -50% of the Ca content was released from the ER. Light stimulation also caused a highly significant increase in the Mg content of the ER; the ratio ofMg uptake to Ca released was -0.7. Our results show unambiguously that the ER is the source of Ca2+ release during cell stimulation and suggest that Mg2+ can nearly balance the charge movement of Ca2+.The mobilization of Ca2" from an intracellular store by a reaction cascade comprising a cell-surface receptor, a guanine nucleotide binding protein, a phospholipase C, and inositol 1,4,5-trisphosphate [Ins(1,4,5)P3] is an important mechanism of signal transduction (1). A great deal of evidence indicates that the endoplasmic reticulum (ER) is the target of Ins(1,4,5)P3 action (2-5) and the organelle involved in the physiological regulation of cytoplasmic Ca2" in nonmuscle cells (6-8), although some authors proposed that the Ins(1,4,5)P3-sensitive Ca2" pool is located in a separate organelle ("calciosome") (9,10). Direct measurements ofthe Ca2+ content and of Ca2+ changes in the ER (or the calciosomes) have been difficult to obtain. Consequently, little is known about the ion movements that must occur during Ca2+ release, to maintain charge balance across the ER membrane. The large sacs of ER in bee photoreceptors (11) are uniquely suitable for addressing these questions because the size makes them clearly identifiable in ultrathin freeze-dried cryosections and allows unambiguous experiments in which the analyzed area is completely within the ER cisternae. Therefore, we determined by electron probe x-ray microanalysis (EPMA) the elemental composition of the ER in situ, in the dark and during light stimulation, that, in invertebrates, is known to be followed by Ins(1,4,5)P3-mediated (12, 13) intracellular Ca2' release (14,15). We quantitated the amount of Ca2' released from the ER during photoresponse and demonstrate an associated uptake of Mg2' into the ER, suggesting that Mg2+ movements make a major contribution toward maintaining electroneutrality during Ca2' release from the ER in bee photoreceptors. Preliminary reports of these findings have been published (16,17). MATERIALS AND METHODSHoney bee drones (Apis mellifera) were kept in the dark at 32°C to 36°C for up to 10 days and fed a concentrated sugar solution. Decapitation and all subsequent manipulations were done under red light (A > 600 nm), which elicits no electrical response of the photoreceptors (18). Thick slices (600-1000 Am) ofthe drone head (19) remained in oxygenated physiological saline containing 170 mM NaCl, 10 mM KCI, 10 mM MgCl2, 1.6 mM CaC12, 10 mM Tris-HCl (pH ...

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Section: Discussionsupporting

confidence: 56%

mentioning

confidence: 99%

Electron probe microanalysis of calcium release and magnesium uptake by endoplasmic reticulum in bee photoreceptors.

Baumann

Walz

Somlyo

et al. 1991

Proc. Natl. Acad. Sci. U.S.A.

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“…Adult heads were fixed and processed according to the method of Baumann and Walz (1989). The fixed tissue was dehydrated in serial changes of ethanol followed by propylene oxide and embedded in Spurr's medium (Polysciences, Inc.).…”

Section: Electron Microscopy and Immunocytochemistrymentioning

confidence: 99%

The cyclophilin homolog NinaA functions as a chaperone, forming a stable complex in vivo with its protein target rhodopsin.

1994

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“…Tissue analyzed by transmission electron microscopy (TEM) was prepared according to the method of Baumann and Walz (1989) with minor modifications. Newly eclosed flies were dissected and fixed for 2 h at room temperature in 0.1 M Na-cacodylate buffer, pH 7.4, containing 2% glutaraldehyde, 2% paraformaldehyde, and 0.07% sucrose.…”

Section: Electron Microscopymentioning

confidence: 99%

“…Specimens were desiccated in a Pelco (Redding, CA) model H critical point drier then mounted on stubs and sputter coated with gold for 4 min in a Polaron SEM coating unit. Specimens were imaged with a Cambridge (Cambridge, United Kingdom) Stereoscan 250 MK2 scanning electron microscope.Tissue analyzed by transmission electron microscopy (TEM) was prepared according to the method of Baumann and Walz (1989) with minor modifications. Newly eclosed flies were dissected and fixed for 2 h at room temperature in 0.1 M Na-cacodylate buffer, pH 7.4, containing 2% glutaraldehyde, 2% paraformaldehyde, and 0.07% sucrose.…”

mentioning

confidence: 99%

Clonal Tests of Conventional Kinesin Function during Cell Proliferation and Differentiation

Brendza

Sheehan

Turner

et al. 2000

MBoC

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Null mutations in the Drosophila Kinesin heavy chain gene (Khc), which are lethal during the second larval instar, have shown that conventional kinesin is critical for fast axonal transport in neurons, but its functions elsewhere are uncertain. To test other tissues, single imaginal cells in young larvae were rendered null for Khc by mitotic recombination. Surprisingly, the null cells produced large clones of adult tissue. The rates of cell proliferation were not reduced, indicating that conventional kinesin is not essential for cell growth or division. This suggests that in undifferentiated cells vesicle transport from the Golgi to either the endoplasmic reticulum or the plasma membrane can proceed at normal rates without conventional kinesin. In adult eye clones produced by null founder cells, there were some defects in differentiation that caused mild ultrastructural changes, but they were not consistent with serious problems in the positioning or transport of endoplasmic reticulum, mitochondria, or vesicles. In contrast, defective cuticle deposition by highly elongated Khc null bristle shafts suggests that conventional kinesin is critical for proper secretory vesicle transport in some cell types, particularly ones that must build and maintain long cytoplasmic extensions. The ubiquity and evolutionary conservation of kinesin heavy chain argue for functions in all cells. We suggest interphase organelle movements away from the cell center are driven by multilayered transport mechanisms; that is, individual organelles can use kinesin-related proteins and myosins, as well as conventional kinesin, to move toward the cell periphery. In this case, other motors can compensate for the loss of conventional kinesin except in cells that have extremely long transport tracks. INTRODUCTIONVesicle transport is important in eukaryotic cells for the addition of material to the plasma membrane, for secretion, and for cell polarity. Active vesicle transport is thought to be driven by mechanochemical enzymes (motor proteins). Motors attach to vesicle membranes and then use ATP hydrolysis to drive unidirectional movement along polar cytoskeletal filaments. Characterized members of the myosin family of motors move toward the barbed or fast-growing ends of actin filaments with the exception of myosin VI, which moves toward the pointed or slow-growing ends (Wells et al., 1999) (reviewed by Sellers and Goodson, 1995). Actin filaments in undifferentiated and in some differentiated cell types are highly concentrated in the cortex (WatermanStorer et al., 1998; reviewed by Cramer, 1999). Cytoplasmic myosins may therefore be important for anchoring or moving vesicles when they are near the plasma membrane (Fath et al., 1994). Motors in the kinesin and dynein families move along microtubules. Characterized dyneins and members of the C-terminal kinesin subfamily move toward microtubule minus ends, whereas other kinesins that act as motors move toward microtubule plus ends (reviewed by Vale and Fletterick, 1997;Hirokawa, 1998;Goldstein and Ya...

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Topography of Ca2+-sequestering endoplasmic reticulum in photoreceptors and pigmented glial cells in the compound eye of the honeybee drone

Cited by 67 publications

References 42 publications

Electron probe microanalysis of calcium release and magnesium uptake by endoplasmic reticulum in bee photoreceptors.

Electron probe microanalysis of calcium release and magnesium uptake by endoplasmic reticulum in bee photoreceptors.

The cyclophilin homolog NinaA functions as a chaperone, forming a stable complex in vivo with its protein target rhodopsin.

Clonal Tests of Conventional Kinesin Function during Cell Proliferation and Differentiation

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