Figure 2. Lipids dictate domain-specific targeting of proteins during phagocytosis.

(A) Structures of the principal phospholipids within the plasma and phagosomal membranes. The phospholipids have a glycerol backbone to which fatty acyl residues are attached at the sn-1 and sn-2 positions. For simplicity, in all cases the common pairing of stearoyl and arachidonyl fatty acids are depicted in the sn-1 and sn-2 positions, respectively. The headgroups that define the lipid species attach to the glycerol backbone at the sn-3 hydroxyl group. The inositol ring of the phosphoinositides can be phosphorylated at any one of three positions (D-3, D-4, and D-5) to yield the various mono-, bis-, and tris-phosphorylated species. DAG and cholesterol (Chol) are also illustrated. PE, phosphatidylethanolamine. (B) The stages of phagocytosis from Figure 1 are shown, with the presence of specific lipids illustrated by the respective colors. Representative proteins attaching to specific lipids are shown, matched by color. Colored segments at stages with multiple lipids do not reflect subdomains or the relative abundance of the different species. Myo10, myosin X. Btk, Bruton agaggaglobulinemia tyrosine kinase.