Serine phosphorylation of FcγRI cytoplasmic domain directs lipid raft localization and interaction with protein 4.1G

Andrew W. Gibson, Xinrui Li, Jianming Wu, Julie G. Baskin, Chander Raman, Jeffrey C. Edberg, Robert P. Kimberly

Research output: Contribution to journalArticlepeer-review

8 Scopus citations


The high-affinity IgG receptor (CD64, FcγRI) has several special capacities, including the receptor-stimulated cleavage of the cell surface B cell-activating factor of the TNF superfamily (TNFSF13B). With the use of the yeast two-hybrid system, we and others have shown that FcγRI interacts with protein 4.1G (EPB41L2). Our mutational analyses identified two required 4.1G-interacting regions in the FcγRI CY and one FcγRI-interacting site in the C-terminus of protein 4.1G. Herein, we explore mechanism(s) that may regulate the interaction between protein 4.1G and FcγRI CY and influence FcγRI membrane mobility and function. We show that FcγRI CY interacts with protein 4.1G in vitro and that FcγRI coimmunoprecipitates protein 4.1G in freshly isolated human PBMC. With the use of immunostaining, we show that FcγRI colocalizes with protein 4.1G in unstimulated U937 cells, in which the FcγRI CY is constitutively serine- phosphorylated, but significant uncoupling occurs following FcγRI cross-linking, suggesting phosphoserine- regulated interaction. In vitro, protein 4.1G interacted preferentially with CK2-phosphorylated FcγRI CY, and compared with WT FcγRI, a nonphosphorylatable FcγRI mutant receptor was excluded from lipid rafts, suggesting a key role for protein 4.1G in targeting phosphorylated FcγRI to rafts. These data are consistent with a phosphoserine-dependent tethering role for protein 4.1G in maintaining FcγRI in lipid rafts and provide insight into the unique phosphoserine-based regulation of receptor signaling by FcγRI CY.

Original languageEnglish (US)
Pages (from-to)97-103
Number of pages7
JournalJournal of Leukocyte Biology
Issue number1
StatePublished - Jan 2012
Externally publishedYes


  • Fc receptors
  • signaling


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