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Published 6 August 2001. doi:10.1083/jcb.200104049
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© The Rockefeller University Press, 0021-9525/2001/8/645 $5.00
The Journal of Cell Biology, Volume 154, Number 3, August 6, 2001 645-658

Article

High resolution mapping of mast cell membranes reveals primary and secondary domains of Fc{epsilon}RI and LAT



Bridget S. Wilson, Janet R. Pfeiffer, Zurab Surviladze, Elizabeth A. Gaudet and Janet M. Oliver

Department of Pathology and Cancer Research and Treatment Center, University of New Mexico Health Sciences Center, Albuquerque, NM 87131

Address correspondence to Bridget S. Wilson, Department of Pathology, University of New Mexico Health Sciences Center, CRF 205, 2325 Camino de Salud, Albuquerque, NM 87131. Tel.: (505) 272-8852. Fax: (505) 272-1435. E-mail bwilson{at}salud.unm.edu

In mast cells, cross-linking the high-affinity IgE receptor (Fc{epsilon}RI) initiates the Lyn-mediated phosphorylation of receptor ITAMs, forming phospho-ITAM binding sites for Syk. Previous immunogold labeling of membrane sheets showed that resting Fc{epsilon}RI colocalize loosely with Lyn, whereas cross-linked Fc{epsilon}RI redistribute into specialized domains (osmiophilic patches) that exclude Lyn, accumulate Syk, and are often bordered by coated pits. Here, the distribution of Fc{epsilon}RI ß is mapped relative to linker for activation of T cells (LAT), Grb2-binding protein 2 (Gab2), two PLC{gamma} isoforms, and the p85 subunit of phosphatidylinositol 3-kinase (PI3-kinase), all implicated in the remodeling of membrane inositol phospholipids. Before activation, PLC{gamma}1 and Gab2 are not strongly membrane associated, LAT occurs in small membrane clusters separate from receptor, and PLC{gamma}2, that coprecipitates with LAT, occurs in clusters and along cytoskeletal cables. After activation, PLC{gamma}2, Gab2, and a portion of p85 colocalize with Fc{epsilon}RI ß in osmiophilic patches. LAT clusters enlarge within 30 s of receptor activation, forming elongated complexes that can intersect osmiophilic patches without mixing. PLC{gamma}1 and another portion of p85 associate preferentially with activated LAT. Supporting multiple distributions of PI3-kinase, Fc{epsilon}RI cross-linking increases PI3-kinase activity in anti-LAT, anti-Fc{epsilon}RIß, and anti-Gab2 immune complexes. We propose that activated mast cells propagate signals from primary domains organized around Fc{epsilon}RIß and from secondary domains, including one organized around LAT.

Key Words: microdomains; PLC{gamma}; phosphatidylinositol 3-kinase; LAT; Gab2


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