Cell Type Specific Expression of Toll-Like Receptors in Human Brains and Implications in Alzheimer’s Disease
Table 1
Overview of Toll-like receptors and their binding ligands.
Receptor
Ligand (origin)
TLR 2
Lipopeptides (surface of gram positive bacteria)[33], peptidoglycan (surface of gram positive bacteria)[34], Zymosan (surface ligand on Fungi)[35], Neisserial porins (gram negative bacteria)[36]
TLR 1/TLR 2
Triacylated lipopeptide (surface of gram positive bacteria)[37]
TLR 2/TLR 6
Diacylated lipopeptide (surface of gram positive bacteria)[38], FSL-1 (synthetic lipopeptide derived from Mycoplasma salivarium) [39], High mobility group box 1 protein (HMGB1) (endogenous DNA-binding protein) [40]
TLR 3
Polyinosinic:polycytidylic acid (Poly(I:C)) (synthetic ligand with similar structure to dsRNA)[41], genomic RNA and dsRNA (Viral RNA)[42], Stathmin (endogenous human protein) [43]
TLR 4
Lipopolysaccharide (LPS) (molecule isolated from cell membrane of gram negative bacteria)[44, 45], Glycosylphosphatidylinositol (GPI) (membrane anchors in Protists)[46], High mobility group box 1 protein (HMGB1) (endogenous DNA-binding protein) [40]
TLR 4/TLR 6
Amyloid beta (peptides derived from the amyloid precursor gene)[47]
TLR 5
Flagellin (structural part of the flagella found on various bacteria)[48]
DNA (virus [52], fungi [53], protists [54] and gram positive [55] and negative bacteria [56]), CpG oligodeoxynucleotides (synthetic single stranded DNA molecules) [57]
