dGRASP-Mediated Noncanonical
Integrin Secretion
Is Required for Drosophila Epithelial
Remodeling
Hans Schotman, Leena Karhinen, and Catherine Rabouille
Developmental Cell 14, 171–182, February 2008
Presented by Ian M. Parnham & Steven de Maat, supervised by Dr. Catherine Rabouille
Oogenesis
• Divided in to early (stages 1–6), mid- (stages 7–10a), and late (stages 10b–
14) oogenesis.
• During oogenesis, the 15 nurse cells, the oocyte, and a surrounding
monolayer of somatically derived follicle cells together comprise the egg
chamber
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Follicle Epithelium (Stage 10)
• BC: Border cells
• NC: Nurse cells
• CC: Centripetal
Cells
• CFC: Cylindrical
Follicular Cells
• In stage 10A the Follicular cells migrate, covering the oocyte and changing
there shape from cubical to columnar.
•In stage 10B follicle cells completely cover oocyte separating nurse cells
from the oocyte, elongating there shape
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What are we going to look at?
Immunofluoresence (IF)
Figure 1
Immunoelectron microscopy (IEM)
ZOC: zone of contact
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Observations
• Architecture of epithelial tissue depends intercellular
junctions and adhesion
• Adhesion with extracellular matrix components at the basal
side is mediated by integrins and integral plasma membrane
αβ heterodimers
• In the wing imaginal discs of Dropsophila larvae, where
αPS1βPS(PS1) and αPS2βPS (PS2) maintain integrity of the
developing wing.
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dGRASP
• dGRASP has been considered bona fide
Golgi proteins.
• Involved in formation and maintenance
of the Golgi
• GrhA (GRASP65/55 homologue) has been
shown to mediate Golgi independent
secretion of AcbA in Dictyostelium.
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Where does dGRASP localize to, during Oocyte
development?
Figure 1
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Aim
Investigate the role of dGRASP
in follicular epithelium
surrounding the developing
oocyte
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Do dGRASP binding partners also translocate towards
the open ZOC during oocyte development?
Figure 1
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Where does the newly localized dGRASP come from?
Figure 2
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Do dgrasp RNA & dGRASP translocate to the same
place?
Figure 2
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Recap
• Stage 10A to 10B: formation of open ZOC
• Stage 10B dGRASP localizes to the open ZOC, almost
no co-localisation with Golgi
• Stage 10B dgrasp mRNA also localizes to the open
ZOC
What does dGRASP do at the open ZOC?
Wild Type
– Stage 10B
dGRASP is important in
maintaining follicular
epithelium integrity
dgrasp100.2
– Stage 10B
Figure 3
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How are integrins deposited
during the progression from stage 10A -> 10B
Integrin αPS1 Is deposited at the open ZOC in stage 10B
Figure 3
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Is Integrin αPS1 also deposited at the open ZOC of
dgrasp100.2 in stage 10B?
Figure 4
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Is Integrin αPS1 also deposited at the open ZOC of
dgrasp100.2 in stage 10B?
Figure 4
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Is βPS also effected by dgrasp100.2?
Figure 4
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Recap
• dGRASP mutant leads to disrupted follicular
epithelium
• αPS1 is deposited at the open ZOC
• αPS1 deposition at the open ZOC is dependent on
dGRASP
• βPS and other adherens junction proteins were
dGRASP independent
• How does dGRASP enable αPS1 deposition?
Is αPS1 deposition Golgi dependent?
Figure 6
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Is αPS1 deposition dSyntaxin-5 dependent?
Figure 6
Conclusion
• In stage 10B dGRASP localizes to the open
ZOC, almost no co-localisation with Golgi
• dGRASP mutant leads to disrupted follicular
epithelium, by interfering with αPS1
deposition at the open ZOC
• dGRASP mediated αPS1 deposition is Golgi
independent
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Discussion
Is αPS1 newly synthesized at the open ZOC?
Figure 5
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Discussion
Is αPS1 newly synthesized at the open ZOC?
Figure 5
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The End
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