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Proc Natl Acad Sci U S A. 2012 Jan 10;109(2):370-7. doi: 10.1073/pnas.1119197109. Epub 2011 Dec 27.

Secreted Wingless-interacting molecule (Swim) promotes long-range signaling by maintaining Wingless solubility.

Author information

1
The Howard Hughes Medical Institute, Stanford University School of Medicine, Stanford, CA 94305, USA.

Abstract

Lipid-modified Wnt/Wingless (Wg) proteins can signal to their target cells in a short- or long-range manner. How these hydrophobic proteins travel through the extracellular environment remains an outstanding question. Here, we report on a Wg binding protein, Secreted Wg-interacting molecule (Swim), that facilitates Wg diffusion through the extracellular matrix. Swim, a putative member of the Lipocalin family of extracellular transport proteins, binds to Wg with nanomolar affinity in a lipid-dependent manner. In quantitative signaling assays, Swim is sufficient to maintain the solubility and activity of purified Wg. In Drosophila, swim RNAi phenotypes resemble wg loss-of-function phenotypes in long-range signaling. We propose that Swim is a cofactor that promotes long-range Wg signaling in vivo by maintaining the solubility of Wg.

PMID:
22203956
PMCID:
PMC3258625
DOI:
10.1073/pnas.1119197109
[Indexed for MEDLINE]
Free PMC Article

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