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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.

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Rescue of scrib discs by ScribGFP transgenes. (A–F) Constructs are driven in  scrib 3 discs. Full-length Scrib (A) restores both polarized organization and disc size. ΔLRR (B), myr-ΔLRR (C), and L223Q (D) rescue neither polarity nor proliferation control. Scrib4 (E) restores polarized and monolayered organization (inset, compare with D and F) but discs are overgrown. ΔPDZ3/4 (F) discs are indistinguishable from WT. (G–M) Constructs are driven in hypomorphic, polarized scrib discs. Myr-ΔLRR does not rescue scrib 4 (G) or scrib j7b3 (H) discs. Expression of Scrib4 or ΔPDZs in scrib 4 (I) or scrib j7b3 (J) provides more complete rescue than these transgenes in  discs. Rescue is further improved at 29° (K, ΔPDZs in scrib 4). Scrib4 overexpression also restores Cor localization (green) and columnar shape to scrib 4 discs (M, compare disc without transgene in L).
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fig6: Rescue of scrib discs by ScribGFP transgenes. (A–F) Constructs are driven in scrib 3 discs. Full-length Scrib (A) restores both polarized organization and disc size. ΔLRR (B), myr-ΔLRR (C), and L223Q (D) rescue neither polarity nor proliferation control. Scrib4 (E) restores polarized and monolayered organization (inset, compare with D and F) but discs are overgrown. ΔPDZ3/4 (F) discs are indistinguishable from WT. (G–M) Constructs are driven in hypomorphic, polarized scrib discs. Myr-ΔLRR does not rescue scrib 4 (G) or scrib j7b3 (H) discs. Expression of Scrib4 or ΔPDZs in scrib 4 (I) or scrib j7b3 (J) provides more complete rescue than these transgenes in discs. Rescue is further improved at 29° (K, ΔPDZs in scrib 4). Scrib4 overexpression also restores Cor localization (green) and columnar shape to scrib 4 discs (M, compare disc without transgene in L).

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)

Rescue of scrib discs by ScribGFP transgenes. (A–F) Constructs are driven in  scrib 3 discs. Full-length Scrib (A) restores both polarized organization and disc size. ΔLRR (B), myr-ΔLRR (C), and L223Q (D) rescue neither polarity nor proliferation control. Scrib4 (E) restores polarized and monolayered organization (inset, compare with D and F) but discs are overgrown. ΔPDZ3/4 (F) discs are indistinguishable from WT. (G–M) Constructs are driven in hypomorphic, polarized scrib discs. Myr-ΔLRR does not rescue scrib 4 (G) or scrib j7b3 (H) discs. Expression of Scrib4 or ΔPDZs in scrib 4 (I) or scrib j7b3 (J) provides more complete rescue than these transgenes in  discs. Rescue is further improved at 29° (K, ΔPDZs in scrib 4). Scrib4 overexpression also restores Cor localization (green) and columnar shape to scrib 4 discs (M, compare disc without transgene in L).
© Copyright Policy
Related In: Results  -  Collection

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

fig6: Rescue of scrib discs by ScribGFP transgenes. (A–F) Constructs are driven in scrib 3 discs. Full-length Scrib (A) restores both polarized organization and disc size. ΔLRR (B), myr-ΔLRR (C), and L223Q (D) rescue neither polarity nor proliferation control. Scrib4 (E) restores polarized and monolayered organization (inset, compare with D and F) but discs are overgrown. ΔPDZ3/4 (F) discs are indistinguishable from WT. (G–M) Constructs are driven in hypomorphic, polarized scrib discs. Myr-ΔLRR does not rescue scrib 4 (G) or scrib j7b3 (H) discs. Expression of Scrib4 or ΔPDZs in scrib 4 (I) or scrib j7b3 (J) provides more complete rescue than these transgenes in discs. Rescue is further improved at 29° (K, ΔPDZs in scrib 4). Scrib4 overexpression also restores Cor localization (green) and columnar shape to scrib 4 discs (M, compare disc without transgene in L).
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