The separation of exocytosis from endocytosis in rat melanotroph membrane capacitance records.

Zupančič, Gregor Drago; Kocmur, L.; Veranič, Peter; Grilc, Sonja; Kordaš, M.; Zorec, Robert

doi:10.1113/jphysiol.1994.sp020382

Cited by 38 publications

(42 citation statements)

References 36 publications

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“…3, available at www.jneurosci.org as supplemental material). The size of the granules, the distance from the plasma membrane, and the area density of the granules in the cytoplasm were measured on randomly sampled sections from the intermediate lobe and were found to be similar to published data (Zupancic et al, 1994). No significant differences in ultrastructure were observed between ␣-neurexin double knock-out mice and littermate controls ( Table 2), indicating that the defect in secretion was not caused by reduced size and/or availability of secretory granules.…”

Section: Nrxn3␣mentioning

confidence: 65%

“…Measurements of the fastest component revealed membrane capacitance changes of ϳ 13 fF in control (n ϭ 10) and ϳ7 fF in DKO cells (n ϭ 20), corresponding to the release of ϳ13 (control) and 7 (DKO) vesicles, respectively (conversion factor of 1 fF per vesicle) (Thomas et al, 1993b), indicating that during short depolarizations the mutant cells secrete only approximately one-half the number of immediately releasable vesicles. The actual size of vesicles in melanotrophs was measured previously by electron microscopy and compared with discrete steps in membrane capacitance (Zupancic et al, 1994). The slower component of secretory responses (depolarization pulses between 40 and 200 ms) was best fit by a linear function in control and mutant cells (Fig.…”

Section: Secretory Activity During the Early Kinetic Phase Of Secretionmentioning

confidence: 99%

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Important Contribution of α-Neurexins to Ca²⁺-Triggered Exocytosis of Secretory Granules

Dudanova¹,

Sedej²,

Ahmad³

et al. 2006

J. Neurosci.

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␣-Neurexins constitute a family of neuronal cell surface molecules that are essential for efficient neurotransmission, because mice lacking two or all three ␣-neurexin genes show a severe reduction of synaptic release. Although analyses of ␣-neurexin knock-outs and transgenic rescue animals suggested an involvement of voltage-dependent Ca 2ϩ channels, it remained unclear whether ␣-neurexins have a general role in Ca 2ϩ -dependent exocytosis and how they may affect Ca 2ϩ channels. Here we show by membrane capacitance measurements from melanotrophs in acute pituitary gland slices that release from endocrine cells is diminished by Ͼ50% in adult ␣-neurexin double knock-out and newborn triple knock-out mice. There is a reduction of the cell volume in mutant melanotrophs; however, no ultrastructural changes in size or intracellular distribution of the secretory granules were observed. Recordings of Ca 2ϩ currents from melanotrophs, transfected human embryonic kidney cells, and brainstem neurons reveal that ␣-neurexins do not affect the activation or inactivation properties of Ca 2ϩ channels directly but may be responsible for coupling them to release-ready vesicles and metabotropic receptors. Our data support a general and essential role for ␣-neurexins in Ca 2ϩ -triggered exocytosis that is similarly important for secretion from neurons and endocrine cells.

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Section: Nrxn3␣mentioning

confidence: 65%

Section: Secretory Activity During the Early Kinetic Phase Of Secretionmentioning

confidence: 99%

Important Contribution of α-Neurexins to Ca²⁺-Triggered Exocytosis of Secretory Granules

Dudanova¹,

Sedej²,

Ahmad³

et al. 2006

J. Neurosci.

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“…In a variety of animal cells, discrete steps in C m have been measured that correlated well with the capacitance estimated from the morphology of vesicles in the cytoplasm (e.g. Lollike et al, 1995;Neher and Marty, 1982;Zupancic et al, 1994). Therefore, it can be assumed that the fluctuations of membrane capacitance report the interaction of transport vesicles with the plasma membrane.…”

Section: Introductionmentioning

confidence: 70%

Unitary exocytotic and endocytotic events in Zea mays L. coleoptile protoplasts

Thiel¹,

Kreft²,

Zorec³

1998

The Plant Journal

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SummaryCell-attached capacitance measurements were used to detect unitary exocytotic and endocytotic events in protoplasts from Zea mays L. coleoptiles with a high-frequency lock-in amplifier. A background noise level of around 70 aF permitted the detection of interacting vesicles with a diameter as small as 60 nm. The distribution of discrete on-steps (exocytosis) was similar to that of off-steps (endocytosis) with a modal values at about 200 aF for both events. From the frequency of endocytotic events (1.5 ⍨ 1.4 min -1 ) it is estimated that 200 min are required for the whole membrane to be ingested in a non-stimulated protoplast.

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“…Melanotrophs contain about 3,000 densecore vesicles that are morphologically docked (42). With an average C m of 2 fF per vesicle (43), this pool of docked dense-core vesicles can readily account for the rapid and slow components of the C m increase. CAPS antibody also may act on unidentified synaptic-like vesicles in melanotrophs.…”

Section: Discussionmentioning

confidence: 99%

Rapid regulated dense-core vesicle exocytosis requires the CAPS protein

Rupnik

Kreft

Sikdar

et al. 2000

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

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Although many proteins essential for regulated neurotransmitter and peptide hormone secretion have been identified, little is understood about their precise roles at specific stages of the multistep pathway of exocytosis. To study the function of CAPS (Ca 2؉ -dependent activator protein for secretion), a protein required for Ca 2؉ -dependent exocytosis of dense-core vesicles, secretory responses in single rat melanotrophs were monitored by patch-clamp membrane capacitance measurements. Flash photolysis of caged Ca 2؉ elicited biphasic capacitance increases consisting of rapid and slow components with distinct Ca 2؉ dependencies. A threshold of Ϸ10 M Ca 2؉ was required to trigger the slow component, while the rapid capacitance increase was recorded already at a intracellular Ca 2؉ activity < 10 M. Both kinetic membrane capacitance components were abolished by botulinum neurotoxin B or E treatment, suggesting involvement of SNARE (soluble N-ethylmaleimide-sensitive factor attachment protein receptor)-dependent vesicle fusion. The rapid but not the slow component was inhibited by CAPS antibody. These results were further clarified by immunocytochemical studies that revealed that CAPS was present on only a subset of dense-core vesicles. Overall, the results indicate that dense-core vesicle exocytosis in melanotrophs occurs by two parallel pathways. The faster pathway exhibits high sensitivity to Ca 2؉ and requires the presence of CAPS, which appears to act at a late stage in the secretory pathway.capacitance ͉ pituitary cells ͉ rat melanotrophs

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The separation of exocytosis from endocytosis in rat melanotroph membrane capacitance records.

Abstract: Rat pars intermedia cells secrete a number of peptides mechanisms controlling this event are still poorly derived from the post-translational processing of understood. pro-opiomelanocortin (POMC), including ,-endorphin,

Cited by 38 publications

References 36 publications

Important Contribution of α-Neurexins to Ca²⁺-Triggered Exocytosis of Secretory Granules

Important Contribution of α-Neurexins to Ca²⁺-Triggered Exocytosis of Secretory Granules

Unitary exocytotic and endocytotic events in Zea mays L. coleoptile protoplasts

Rapid regulated dense-core vesicle exocytosis requires the CAPS protein

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The separation of exocytosis from endocytosis in rat melanotroph membrane capacitance records.

Abstract: Rat pars intermedia cells secrete a number of peptides mechanisms controlling this event are still poorly derived from the post-translational processing of understood. pro-opiomelanocortin (POMC), including ,-endorphin,

Cited by 38 publications

References 36 publications

Important Contribution of α-Neurexins to Ca2+-Triggered Exocytosis of Secretory Granules

Important Contribution of α-Neurexins to Ca2+-Triggered Exocytosis of Secretory Granules

Unitary exocytotic and endocytotic events in Zea mays L. coleoptile protoplasts

Rapid regulated dense-core vesicle exocytosis requires the CAPS protein

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Product

Resources

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Important Contribution of α-Neurexins to Ca²⁺-Triggered Exocytosis of Secretory Granules

Important Contribution of α-Neurexins to Ca²⁺-Triggered Exocytosis of Secretory Granules