Use of a photoactivatable taxol analogue to identify unique cellular targets in murine macrophages: identification of murine CD18 as a major taxol-binding protein and a role for Mac-1 in taxol-induced gene expression.
Taxol, a potent antitumor agent that binds beta-tubulin and promotes microtubule assembly, results in mitotic arrest at the G2/M phase of the cell cycle. More recently, Taxol was shown to be a potent LPS mimetic in murine, but not in human macrophages, stimulating signaling pathways and gene expression indistinguishably from LPS. Although structurally unrelated to LPS, Taxol's LPS-mimetic activities are blocked by inactive structural analogues of LPS, indicating that despite the species-restricted effects of Taxol, LPS and Taxol share a common receptor/signaling complex that might be important in LPS-induced human diseases. To identify components of the putatively shared Taxol/LPS receptor, a novel, photoactivatable Taxol analogue was employed to identify unique Taxol-binding proteins in murine macrophage membranes. Seven major Taxol-binding proteins, ranging from approximately 50 to 200 kDa, were detected. Although photoactivatable Taxol analogue failed to bind to CD14, the prominent Taxol-binding protein was identified as CD18, the approximately 96-kDa common component of the beta2 integrin family. This finding was supported by the concomitant failure of macrophage membranes from Mac-1 knockout mice to express immunoreactive CD18 and the major Taxol-binding protein. In addition, Taxol-induced IL-12 p40 mRNA was markedly reduced in Mac-1 knockout macrophages and anti-Mac-1 Ab blocked secretion of IL-12 p70 in Taxol- and LPS-stimulated macrophages. Since CD18 has been described as a participant in LPS-induced binding and signal transduction, these data support the hypothesis that the interaction of murine CD18 with Taxol is involved in its proinflammatory activity.
Bhat
N
N
Department of Microbiology and Immunology, Uniformed Services University of the Health Sciences, Bethesda, MD 20814, USA.
Perera
P Y
PY
Carboni
J M
JM
Blanco
J
J
Golenbock
D T
DT
Mayadas
T N
TN
Vogel
S N
SN
D000595:Amino Acid Sequence; D000818:Animals; D018821:CD18 Antigens / Q000302:isolation & purification / Q000378:metabolism*; D016466:CHO Cells; D002352:Carrier Proteins / Q000302:isolation & purification / Q000378:metabolism*; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D006224:Cricetinae; D005786:Gene Expression Regulation / Q000276:immunology*; D006801:Humans; D007106:Immune Sera / Q000494:pharmacology; D018664:Interleukin-12 / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism; D008070:Lipopolysaccharides / Q000494:pharmacology; D016177:Macrophage-1 Antigen / Q000235:genetics / Q000276:immunology / Q000502:physiology*; D017737:Macrophages, Peritoneal / Q000187:drug effects / Q000276:immunology / Q000378:metabolism*; D051379:Mice; D008809:Mice, Inbred C3H; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008969:Molecular Sequence Data; D017239:Paclitaxel / Q000031:analogs & derivatives* / Q000378:metabolism* / Q000494:pharmacology; D019920:Photoaffinity Labels / Q000378:metabolism; D012333:RNA, Messenger / Q000096:biosynthesis
D018821:CD18 Antigens; D002352:Carrier Proteins; D007106:Immune Sera; D008070:Lipopolysaccharides; D016177:Macrophage-1 Antigen; D019920:Photoaffinity Labels; D012333:RNA, Messenger; D018664:Interleukin-12; D017239:Paclitaxel