A quantification of pathway components supports a novel model of hedgehog signal transduction

Shohreh F. Farzan, Melanie A. Stegman, Stacey K. Ogden, Manuel Ascano, Kendall E. Black, Ofelia Tacchelly, David J Robbins

Research output: Contribution to journalArticle

9 Citations (Scopus)

Abstract

The secreted protein Hedgehog (Hh) plays a critical instructional role during metazoan development. In Drosophila, Hh signaling is interpreted by a set of conserved, downstream effectors that differentially localize and interact to regulate the stability and activity of the transcription factor Cubitus interruptus. Two essential models that integrate genetic, cell biological, and biochemical information have been proposed to explain how these signaling components relate to one another within the cellular context. As the molar ratios of the signaling effectors required in each of these models are quite different, quantitating the cellular ratio of pathway components could distinguish these two models. Here, we address this important question using a set of purified protein standards to perform a quantitative analysis of Drosophila cell lysates for each downstream pathway component. We determine each component's steady-state concentration within a given cell, demonstrate the molar ratio of Hh signaling effectors differs more than two orders of magnitude and that this ratio is conserved in vivo. We find that the G-protein-coupled transmembrane protein Smoothened, an activating component, is present in limiting amounts, while a negative pathway regulator, Suppressor of Fused, is present in vast molar excess. Interestingly, despite large differences in the steady-state ratio, all downstream signaling components exist in an equimolar membrane-associated complex. We use these quantitative results to re-evaluate the current models ofHhsignaling and now propose a novel model of signaling that accounts for the stoichiometric differences observed between various Hh pathway components.

Original languageEnglish
Pages (from-to)28874-28884
Number of pages11
JournalJournal of Biological Chemistry
Volume284
Issue number42
DOIs
StatePublished - Oct 16 2009
Externally publishedYes

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Signal transduction
Hedgehogs
Signal Transduction
Drosophila
Hedgehog Proteins
Genetic Models
GTP-Binding Proteins
Transcription Factors
Membranes
Proteins
Chemical analysis

ASJC Scopus subject areas

  • Biochemistry
  • Cell Biology
  • Molecular Biology

Cite this

A quantification of pathway components supports a novel model of hedgehog signal transduction. / Farzan, Shohreh F.; Stegman, Melanie A.; Ogden, Stacey K.; Ascano, Manuel; Black, Kendall E.; Tacchelly, Ofelia; Robbins, David J.

In: Journal of Biological Chemistry, Vol. 284, No. 42, 16.10.2009, p. 28874-28884.

Research output: Contribution to journalArticle

Farzan, SF, Stegman, MA, Ogden, SK, Ascano, M, Black, KE, Tacchelly, O & Robbins, DJ 2009, 'A quantification of pathway components supports a novel model of hedgehog signal transduction', Journal of Biological Chemistry, vol. 284, no. 42, pp. 28874-28884. https://doi.org/10.1074/jbc.M109.041608
Farzan SF, Stegman MA, Ogden SK, Ascano M, Black KE, Tacchelly O et al. A quantification of pathway components supports a novel model of hedgehog signal transduction. Journal of Biological Chemistry. 2009 Oct 16;284(42):28874-28884. https://doi.org/10.1074/jbc.M109.041608
Farzan, Shohreh F. ; Stegman, Melanie A. ; Ogden, Stacey K. ; Ascano, Manuel ; Black, Kendall E. ; Tacchelly, Ofelia ; Robbins, David J. / A quantification of pathway components supports a novel model of hedgehog signal transduction. In: Journal of Biological Chemistry. 2009 ; Vol. 284, No. 42. pp. 28874-28884.
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