|
1000
|
Abstract/Summary
|
-
CAPSULE:
BACKGROUND: CEACAM3-mediated phagocytosis is an innate mechanism to eliminate CEACAM-binding pathogenic bacteria.
RESULTS: Biochemical analyses and FRET-FLIM imaging reveal the direct binding of the adaptor protein Grb14 to the tyrosine-phosphorylated cytoplasmic domain of CEACAM3, and this interaction limits phagocytosis.
CONCLUSION: Grb14 is a negative regulator of CEACAM3-mediated phagocytosis.
SIGNIFICANCE: Deciphering CEACAM3 interaction partners illuminates the minimal set of cellular factors controlling phagocytosis.
-
Carcinoembryonic antigen-related cell adhesion molecule 3 (CEACAM3) is a phagocytic receptor on human granulocytes, which mediates the opsonin-independent recognition and internalization of a restricted set of Gram-negative bacteria such as Neisseria gonorrhoeae. In an unbiased screen using a SH2 domain microarray we identified the SH2 domain of growth factor receptor-bound protein 14 (Grb14) as a novel binding partner of CEACAM3. Biochemical assays and microscopic studies demonstrated that the Grb14 SH2 domain promoted the rapid recruitment of this adaptor protein to the immunoreceptor-based activation motif (ITAM)-like sequence within the cytoplasmic domain of CEACAM3. Furthermore, FRET-FLIM analyses confirmed the direct association of Grb14 and CEACAM3 in intact cells at the sites of bacteria-host cell contact. Knockdown of endogenous Grb14 by RNA interference as well as Grb14 overexpression indicate an inhibitory role for this adapter protein in CEACAM3-mediated phagocytosis. Therefore, Grb14 is the first negative regulator of CEACAM3-initiated bacterial phagocytosis and might help to focus granulocyte responses to the subcellular sites of pathogen-host cell contact.
|
