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Partitioning and Exocytosis of Secretory Granules during Division of PC12 Cells.

Bukoreshtliev NV, Hodneland E, Eichler TW, Eifart P, Rustom A, Gerdes HH - Int J Cell Biol (2012)

Bottom Line: By combining ultrastructural analyses and time-lapse microscopy, we here show that, in dividing PC12 cells, the prominent peripheral localization of secretory granules is retained during prophase but clearly reduced during prometaphase, ending up with only few peripherally localized secretory granules in metaphase cells.During anaphase and telophase, secretory granules exhibited a pronounced movement towards the cell midzone and, evidently, their tracks colocalized with spindle microtubules.During cytokinesis, secretory granules were excluded from the midbody and accumulated at the bases of the intercellular bridge.

View Article: PubMed Central - PubMed

Affiliation: Interdisciplinary Center for Neurosciences (IZN), Department of Neurobiology, University of Heidelberg, INF 364, 69120 Heidelberg, Germany.

ABSTRACT
The biogenesis, maturation, and exocytosis of secretory granules in interphase cells have been well documented, whereas the distribution and exocytosis of these hormone-storing organelles during cell division have received little attention. By combining ultrastructural analyses and time-lapse microscopy, we here show that, in dividing PC12 cells, the prominent peripheral localization of secretory granules is retained during prophase but clearly reduced during prometaphase, ending up with only few peripherally localized secretory granules in metaphase cells. During anaphase and telophase, secretory granules exhibited a pronounced movement towards the cell midzone and, evidently, their tracks colocalized with spindle microtubules. During cytokinesis, secretory granules were excluded from the midbody and accumulated at the bases of the intercellular bridge. Furthermore, by measuring exocytosis at the single granule level, we showed, that during all stages of cell division, secretory granules were competent for regulated exocytosis. In conclusion, our data shed new light on the complex molecular machinery of secretory granule redistribution during cell division, which facilitates their release from the F-actin-rich cortex and active transport along spindle microtubules.

No MeSH data available.


Ultrastructural analysis of the distribution of SGs during late stages of mitosis. Synchronized PC12 cell populations were processed for TEM. Shown are cells at anaphase (A) and telophase (B) and the respective magnified boxed areas on the right compare the density of SGs in the midzone ((A1)/(B1)) and the polar periphery ((A2)/(B3)). Please note that SGs are preferentially distributed in the cell midzone. Panel B2 is a magnification of the boxed region in panel B. Please note the close association of an SG (red arrow) with a microtubule fiber (red asterisk) and an apparent linker structure (red arrowhead) reminiscent of a motor protein. CH, chromosome. Scale bars, panels (A) and (B), 5 μm; panels (A1), (A2), (B1), and (B3), 500 nm; panel (B2), 100 nm.
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fig6: Ultrastructural analysis of the distribution of SGs during late stages of mitosis. Synchronized PC12 cell populations were processed for TEM. Shown are cells at anaphase (A) and telophase (B) and the respective magnified boxed areas on the right compare the density of SGs in the midzone ((A1)/(B1)) and the polar periphery ((A2)/(B3)). Please note that SGs are preferentially distributed in the cell midzone. Panel B2 is a magnification of the boxed region in panel B. Please note the close association of an SG (red arrow) with a microtubule fiber (red asterisk) and an apparent linker structure (red arrowhead) reminiscent of a motor protein. CH, chromosome. Scale bars, panels (A) and (B), 5 μm; panels (A1), (A2), (B1), and (B3), 500 nm; panel (B2), 100 nm.

Mentions: Similar immunofluorescence and confocal analysis of anaphase and telophase PC12 cells revealed that the majority of SGs was accumulated in the cell midzone (Figures 5(A)–5(C1) and Figures 5(D)–5(F1), resp.). As depicted in Figures 5(B1)/5(C1) and 5(E1)/5(F1), during these stages a frequent colocalisation of SGs (arrows) and spindle microtubules (arrowheads) was observed. This redistribution of SGs in the cell midzone was also evident at the ultrastructural level (please see Figure 6). SGs were also frequently observed in close proximity to microtubules at the ultrastructural level (Figure 6(B2)) with an apparent linker structure, reminiscent of a motor protein (Figure 6(B2), red arrowhead).


Partitioning and Exocytosis of Secretory Granules during Division of PC12 Cells.

Bukoreshtliev NV, Hodneland E, Eichler TW, Eifart P, Rustom A, Gerdes HH - Int J Cell Biol (2012)

Ultrastructural analysis of the distribution of SGs during late stages of mitosis. Synchronized PC12 cell populations were processed for TEM. Shown are cells at anaphase (A) and telophase (B) and the respective magnified boxed areas on the right compare the density of SGs in the midzone ((A1)/(B1)) and the polar periphery ((A2)/(B3)). Please note that SGs are preferentially distributed in the cell midzone. Panel B2 is a magnification of the boxed region in panel B. Please note the close association of an SG (red arrow) with a microtubule fiber (red asterisk) and an apparent linker structure (red arrowhead) reminiscent of a motor protein. CH, chromosome. Scale bars, panels (A) and (B), 5 μm; panels (A1), (A2), (B1), and (B3), 500 nm; panel (B2), 100 nm.
© Copyright Policy - open-access
Related In: Results  -  Collection

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fig6: Ultrastructural analysis of the distribution of SGs during late stages of mitosis. Synchronized PC12 cell populations were processed for TEM. Shown are cells at anaphase (A) and telophase (B) and the respective magnified boxed areas on the right compare the density of SGs in the midzone ((A1)/(B1)) and the polar periphery ((A2)/(B3)). Please note that SGs are preferentially distributed in the cell midzone. Panel B2 is a magnification of the boxed region in panel B. Please note the close association of an SG (red arrow) with a microtubule fiber (red asterisk) and an apparent linker structure (red arrowhead) reminiscent of a motor protein. CH, chromosome. Scale bars, panels (A) and (B), 5 μm; panels (A1), (A2), (B1), and (B3), 500 nm; panel (B2), 100 nm.
Mentions: Similar immunofluorescence and confocal analysis of anaphase and telophase PC12 cells revealed that the majority of SGs was accumulated in the cell midzone (Figures 5(A)–5(C1) and Figures 5(D)–5(F1), resp.). As depicted in Figures 5(B1)/5(C1) and 5(E1)/5(F1), during these stages a frequent colocalisation of SGs (arrows) and spindle microtubules (arrowheads) was observed. This redistribution of SGs in the cell midzone was also evident at the ultrastructural level (please see Figure 6). SGs were also frequently observed in close proximity to microtubules at the ultrastructural level (Figure 6(B2)) with an apparent linker structure, reminiscent of a motor protein (Figure 6(B2), red arrowhead).

Bottom Line: By combining ultrastructural analyses and time-lapse microscopy, we here show that, in dividing PC12 cells, the prominent peripheral localization of secretory granules is retained during prophase but clearly reduced during prometaphase, ending up with only few peripherally localized secretory granules in metaphase cells.During anaphase and telophase, secretory granules exhibited a pronounced movement towards the cell midzone and, evidently, their tracks colocalized with spindle microtubules.During cytokinesis, secretory granules were excluded from the midbody and accumulated at the bases of the intercellular bridge.

View Article: PubMed Central - PubMed

Affiliation: Interdisciplinary Center for Neurosciences (IZN), Department of Neurobiology, University of Heidelberg, INF 364, 69120 Heidelberg, Germany.

ABSTRACT
The biogenesis, maturation, and exocytosis of secretory granules in interphase cells have been well documented, whereas the distribution and exocytosis of these hormone-storing organelles during cell division have received little attention. By combining ultrastructural analyses and time-lapse microscopy, we here show that, in dividing PC12 cells, the prominent peripheral localization of secretory granules is retained during prophase but clearly reduced during prometaphase, ending up with only few peripherally localized secretory granules in metaphase cells. During anaphase and telophase, secretory granules exhibited a pronounced movement towards the cell midzone and, evidently, their tracks colocalized with spindle microtubules. During cytokinesis, secretory granules were excluded from the midbody and accumulated at the bases of the intercellular bridge. Furthermore, by measuring exocytosis at the single granule level, we showed, that during all stages of cell division, secretory granules were competent for regulated exocytosis. In conclusion, our data shed new light on the complex molecular machinery of secretory granule redistribution during cell division, which facilitates their release from the F-actin-rich cortex and active transport along spindle microtubules.

No MeSH data available.