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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.


Model of SG partitioning during division of PC12 cells. The scheme summarizes the observed redistribution of SGs during cell division.
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Related In: Results  -  Collection


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fig11: Model of SG partitioning during division of PC12 cells. The scheme summarizes the observed redistribution of SGs during cell division.

Mentions: In this study, the partitioning and dynamics of SGs during cell division of neuroendocrine PC12 cells was comprehensively analyzed. The data presented here concur in substance with the drawn conclusions of Tooze and Burke on the inheritance of SGs in At20 cells [14] but, in extension of their study, provide detailed and direct insights into the dynamics and distribution of SGs during the division process. These straight insights were in particular gained from time-lapse imaging of SGs and microtubules during the consecutive phases of cell division. Based on our results, we propose the following model for the redistribution of SGs during cell division (Figure 11). During interphase, approximately 70% of all SGs are restricted to the F-actin-rich cell cortex. Accordingly, this fraction is referred to as morphologically docked (Figure 11). During prometaphase, the morphologically docked SGs are liberated from the cell cortex and spread throughout the cell. During metaphase, nearly all SGs are distributed nearly homogenously in the cytoplasm (Figure 11). At the onset of anaphase, SGs associate with and move along the spindle microtubules to reach the cell midzone. This results in an initial accumulation of SGs at the cell equator, juxtaposed to the nascent contractile ring. Subsequently, they spread from there over the entire cell midzone, occupying the space liberated by the pole-directed movement of the chromosomes (Figure 11). During cytokinesis, the progressive constriction of the contractile ring results in the exclusion of SGs from the midbody and their subsequent accumulation at the bases of the intercellular bridge. Although SGs exhibit bidirectional, presumably microtubule-dependent movement at the bases of the intercellular bridge, the accumulations at these sites are retained until late cytokinesis (Figure 11). The only significant difference in the inheritance modes of SGs in AtT20 and PC12 cells is observed during cytokinesis: SGs in AtT20 cells accumulate predominantly in the midbody, while SGs in PC12 cells accumulate at the bases of the cytokinesis bridge and are excluded from the midbody. This most probably reflects cell-specific differences in architecture and the biomechanics of the constriction of the midbody structure itself.


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)

Model of SG partitioning during division of PC12 cells. The scheme summarizes the observed redistribution of SGs during cell division.
© Copyright Policy - open-access
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3375158&req=5

fig11: Model of SG partitioning during division of PC12 cells. The scheme summarizes the observed redistribution of SGs during cell division.
Mentions: In this study, the partitioning and dynamics of SGs during cell division of neuroendocrine PC12 cells was comprehensively analyzed. The data presented here concur in substance with the drawn conclusions of Tooze and Burke on the inheritance of SGs in At20 cells [14] but, in extension of their study, provide detailed and direct insights into the dynamics and distribution of SGs during the division process. These straight insights were in particular gained from time-lapse imaging of SGs and microtubules during the consecutive phases of cell division. Based on our results, we propose the following model for the redistribution of SGs during cell division (Figure 11). During interphase, approximately 70% of all SGs are restricted to the F-actin-rich cell cortex. Accordingly, this fraction is referred to as morphologically docked (Figure 11). During prometaphase, the morphologically docked SGs are liberated from the cell cortex and spread throughout the cell. During metaphase, nearly all SGs are distributed nearly homogenously in the cytoplasm (Figure 11). At the onset of anaphase, SGs associate with and move along the spindle microtubules to reach the cell midzone. This results in an initial accumulation of SGs at the cell equator, juxtaposed to the nascent contractile ring. Subsequently, they spread from there over the entire cell midzone, occupying the space liberated by the pole-directed movement of the chromosomes (Figure 11). During cytokinesis, the progressive constriction of the contractile ring results in the exclusion of SGs from the midbody and their subsequent accumulation at the bases of the intercellular bridge. Although SGs exhibit bidirectional, presumably microtubule-dependent movement at the bases of the intercellular bridge, the accumulations at these sites are retained until late cytokinesis (Figure 11). The only significant difference in the inheritance modes of SGs in AtT20 and PC12 cells is observed during cytokinesis: SGs in AtT20 cells accumulate predominantly in the midbody, while SGs in PC12 cells accumulate at the bases of the cytokinesis bridge and are excluded from the midbody. This most probably reflects cell-specific differences in architecture and the biomechanics of the constriction of the midbody structure itself.

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.