Limits...
Domains controlling cell polarity and proliferation in the Drosophila tumor suppressor Scribble.

Zeitler J, Hsu CP, Dionne H, Bilder D - J. Cell Biol. (2004)

Bottom Line: The PDZ domains, which recruit the LRR to the junctional complex, are dispensable for overall epithelial organization.PDZ domain absence leads to mild polarity defects accompanied by moderate overproliferation, but the PDZ domains alone are insufficient to provide any Scrib function in mutant discs.We suggest a model in which Scrib, via the activity of the LRR, governs proliferation primarily by regulating apicobasal polarity.

View Article: PubMed Central - PubMed

Affiliation: Department of Molecular and Cell Biology, University of California Berkeley, Berkeley, CA 94720, USA.

ABSTRACT
Cell polarity and cell proliferation can be coupled in animal tissues, but how they are coupled is not understood. In Drosophila imaginal discs, loss of the neoplastic tumor suppressor gene scribble (scrib), which encodes a multidomain scaffolding protein, disrupts epithelial organization and also causes unchecked proliferation. Using an allelic series of mutations along with rescuing transgenes, we have identified domain requirements for polarity, proliferation control, and other Scrib functions. The leucine-rich repeats (LRR) tether Scrib to the plasma membrane, are both necessary and sufficient to organize a polarized epithelial monolayer, and are required for all proliferation control. The PDZ domains, which recruit the LRR to the junctional complex, are dispensable for overall epithelial organization. PDZ domain absence leads to mild polarity defects accompanied by moderate overproliferation, but the PDZ domains alone are insufficient to provide any Scrib function in mutant discs. We suggest a model in which Scrib, via the activity of the LRR, governs proliferation primarily by regulating apicobasal polarity.

Show MeSH

Related in: MedlinePlus

Construction and localization of ScribGFP transgenes. (A) Diagram of UAS-driven transgenes. (B–G) Localization of ptcGal4-driven ScribGFP proteins (green, phalloidin in red) in WT wing discs. Full-length Scrib (B) is basolaterally restricted and enriched at the SJ, whereas ΔLRR (C) and L223Q (E) are found in the cytoplasm. Membrane attachment with some SJ enrichment is seen with myr-ΔLRR (D). Scrib4 (F) is localized broadly along basolateral membranes without evident polarization. ΔPDZ3/4 (G) is found at SJs, similar to full-length Scrib.
© Copyright Policy
Related In: Results  -  Collection


getmorefigures.php?uid=PMC2172630&req=5

fig5: Construction and localization of ScribGFP transgenes. (A) Diagram of UAS-driven transgenes. (B–G) Localization of ptcGal4-driven ScribGFP proteins (green, phalloidin in red) in WT wing discs. Full-length Scrib (B) is basolaterally restricted and enriched at the SJ, whereas ΔLRR (C) and L223Q (E) are found in the cytoplasm. Membrane attachment with some SJ enrichment is seen with myr-ΔLRR (D). Scrib4 (F) is localized broadly along basolateral membranes without evident polarization. ΔPDZ3/4 (G) is found at SJs, similar to full-length Scrib.

Mentions: We initially asked whether the LRR is indeed critical for all Scrib functions. Expression of Scrib lacking the LRR but retaining all four PDZ domains (UAS-ΔLRR) in WT discs reveals cytoplasmic and unpolarized localization, with no membrane association apparent (Fig. 5 C). When expressed in scrib discs, this construct has no rescuing activity: cells remain unpolarized, and disc overgrowth is unaffected (Fig. 6 B and Fig. 2 G). Because the phenotypically strong scrib 1 missense mutation (L223Q) also maps to the LRR, we assayed a transgene containing this mutation. Like UAS-ΔLRR, UAS-L223Q is predominantly cytoplasmic and mutant discs expressing this construct show no signs of rescue (Fig. 5 E and Fig. 6 D). Together, these experiments demonstrate the importance of the LRR for Scrib subcellular localization as well as both polarity and proliferation control activity.


Domains controlling cell polarity and proliferation in the Drosophila tumor suppressor Scribble.

Zeitler J, Hsu CP, Dionne H, Bilder D - J. Cell Biol. (2004)

Construction and localization of ScribGFP transgenes. (A) Diagram of UAS-driven transgenes. (B–G) Localization of ptcGal4-driven ScribGFP proteins (green, phalloidin in red) in WT wing discs. Full-length Scrib (B) is basolaterally restricted and enriched at the SJ, whereas ΔLRR (C) and L223Q (E) are found in the cytoplasm. Membrane attachment with some SJ enrichment is seen with myr-ΔLRR (D). Scrib4 (F) is localized broadly along basolateral membranes without evident polarization. ΔPDZ3/4 (G) is found at SJs, similar to full-length Scrib.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2172630&req=5

fig5: Construction and localization of ScribGFP transgenes. (A) Diagram of UAS-driven transgenes. (B–G) Localization of ptcGal4-driven ScribGFP proteins (green, phalloidin in red) in WT wing discs. Full-length Scrib (B) is basolaterally restricted and enriched at the SJ, whereas ΔLRR (C) and L223Q (E) are found in the cytoplasm. Membrane attachment with some SJ enrichment is seen with myr-ΔLRR (D). Scrib4 (F) is localized broadly along basolateral membranes without evident polarization. ΔPDZ3/4 (G) is found at SJs, similar to full-length Scrib.
Mentions: We initially asked whether the LRR is indeed critical for all Scrib functions. Expression of Scrib lacking the LRR but retaining all four PDZ domains (UAS-ΔLRR) in WT discs reveals cytoplasmic and unpolarized localization, with no membrane association apparent (Fig. 5 C). When expressed in scrib discs, this construct has no rescuing activity: cells remain unpolarized, and disc overgrowth is unaffected (Fig. 6 B and Fig. 2 G). Because the phenotypically strong scrib 1 missense mutation (L223Q) also maps to the LRR, we assayed a transgene containing this mutation. Like UAS-ΔLRR, UAS-L223Q is predominantly cytoplasmic and mutant discs expressing this construct show no signs of rescue (Fig. 5 E and Fig. 6 D). Together, these experiments demonstrate the importance of the LRR for Scrib subcellular localization as well as both polarity and proliferation control activity.

Bottom Line: The PDZ domains, which recruit the LRR to the junctional complex, are dispensable for overall epithelial organization.PDZ domain absence leads to mild polarity defects accompanied by moderate overproliferation, but the PDZ domains alone are insufficient to provide any Scrib function in mutant discs.We suggest a model in which Scrib, via the activity of the LRR, governs proliferation primarily by regulating apicobasal polarity.

View Article: PubMed Central - PubMed

Affiliation: Department of Molecular and Cell Biology, University of California Berkeley, Berkeley, CA 94720, USA.

ABSTRACT
Cell polarity and cell proliferation can be coupled in animal tissues, but how they are coupled is not understood. In Drosophila imaginal discs, loss of the neoplastic tumor suppressor gene scribble (scrib), which encodes a multidomain scaffolding protein, disrupts epithelial organization and also causes unchecked proliferation. Using an allelic series of mutations along with rescuing transgenes, we have identified domain requirements for polarity, proliferation control, and other Scrib functions. The leucine-rich repeats (LRR) tether Scrib to the plasma membrane, are both necessary and sufficient to organize a polarized epithelial monolayer, and are required for all proliferation control. The PDZ domains, which recruit the LRR to the junctional complex, are dispensable for overall epithelial organization. PDZ domain absence leads to mild polarity defects accompanied by moderate overproliferation, but the PDZ domains alone are insufficient to provide any Scrib function in mutant discs. We suggest a model in which Scrib, via the activity of the LRR, governs proliferation primarily by regulating apicobasal polarity.

Show MeSH
Related in: MedlinePlus