PubMed Journals: Blood

  Source:		PMID: 10477722

    		Blood. 1999 Sep 15;94(6):1933-42.
			Identification of a 14-3-3 binding sequence
			in the common beta chain of the
			granulocyte-macrophage colony-stimulating
			factor (GM-CSF), interleukin-3 (IL-3), and
			IL-5 receptors that is serine-phosphorylated
			by GM-CSF.

			Stomski FC(1), Dottore M, Winnall W, Guthridge
			MA, Woodcock J, Bagley CJ, Thomas DT, Andrews
			RK, Berndt MC, Lopez AF.

			Author Information
			(1) The Cytokine Receptor Laboratory, The
			Hanson Centre for Cancer Research and Institute
			of Medical and Veterinary Science, Adelaide,

			The common beta chain (beta(c)) of the
			granulocyte-macrophage colony-stimulating
			factor (GM-CSF), interleukin-3 (IL-3), and
			IL-5 receptors is the major signaling subunit
			of these receptors coupling ligand binding
			to multiple biological activities. It is
			thought that these multiple functions arise
			as a consequence of the recruitment of specific
			signaling molecules to tyrosine-phosphorylated
			residues in the cytoplasmic domain of beta(c).
			However, the contribution of serine phosphorylation
			in beta(c) to the recruitment of signaling
			molecules is not known. We show here the
			identification of a phosphoserine motif
			in the cytoplasmic domain of beta(c) that
			interacts with the adaptor protein 14-3-3zeta.
			Coimmunoprecipitation and pull-down experiments
			with a glutathione S-transferase (GST):14-3-3zeta
			fusion protein showed that 14-3-3 directly associates
			with beta(c) but not the GM-CSF receptor
			alpha chain. C-terminal truncation mutants of
			beta(c) further showed that a region between
			amino acids 544 and 626 in beta(c) was required
			for its association with 14-3-3zeta. This
			region contains the sequence (582)HSRSLP(587),
			which closely resembles the RSXSXP (where
			S is phosphorylated) consensus 14-3-3 binding
			site identified in a number of signaling
			molecules, including Raf-1. Significantly,
			substitution of (582)HSRSLP(587) for EFAAAA
			completely abolished interaction of beta(c)
			with GST-14-3-3zeta. Furthermore, the interaction
			of beta(c) with GST-14-3-3 was greatly reduced
			in the presence of a peptide containing
			the 14-3-3 binding site, but only when (585)Ser
			was phosphorylated. Direct binding experiments
			showed that the peptide containing phosphorylated
			(585)Ser bound 14-3-3zeta with an affinity
			of 150 nmol/L. To study the regulation of
			(585)S phosphorylation in vivo, we raised
			antibodies that specifically recognized
			(585)Ser-phosphorylated beta(c). Using these
			antibodies, we showed that GM-CSF stimulation
			strongly upregulated (585)Ser phosphorylation
			in M1 myeloid leukemic cells. The proximity
			of the SHC-binding site ((577)Tyr) to the
			14-3-3-binding site ((582)HSRSLP(587)) and
			their conservation between mouse, rat, and
			human beta(c) but not in other cytokine
			receptors suggest that they form a distinct
			motif that may subserve specialized functions
			associated with the GM-CSF, IL-3, and IL-5

			PMID: 10477722 [Indexed for MEDLINE]

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