Adhesion-activating phorbol ester increases the mobility of leukocyte integrin LFA-1 in cultured lymphocytes.
Lymphocytes activate adhesion to intracellular adhesion mlecule 1 (ICAM-1) via leukocyte function associated antigen 1 (LFA-1), their major beta 2 integrin, in response to PMA (phorbol 12-myristate 13-acetate) without an increase in the number of receptors expressed. The molecular details of the mechanism are unknown. To determine the effect of PMA activation on LFA-1 movement within the plasma membrane, we used the single particle tracking technique to measure the diffusion rate of LFA-1 molecules on EBV-transformed B cells before and after PMA activation. Diffusion of LFA-1 on unactivated cells was restricted compared to CR1 (CD35), another transmembrane protein of equivalent size. PMA caused a 10-fold increase in the diffusion rate of LFA-1 without any effect on CD35. The increased LFA-1 motion induced by PMA was random, not directed, indicating that it was due to a release of constraints rather than the application of forces. The diffusion rates of LFA-1 are consistent with cytoskeletal attachment before and free diffusion after PMA. Cytochalasin D led to an equivalent increase in mobility and, at low doses, stimulated adhesion, implying that the nonadhesive state of LFA-1 is actively maintained by the lymphocyte cytoskeleton.
Kucik
D F
DF
Department of Internal Medicine, Washington University School of Medicine, St. Louis, MO 63110, USA, kuck@id.wustl.edu
Dustin
M L
ML
Miller
J M
JM
Brown
E J
EJ
D001692:Biological Transport; D002273:Carcinogens / Q000494:pharmacology*; D002448:Cell Adhesion / Q000187:drug effects; D002462:Cell Membrane / Q000378:metabolism* / Q000648:ultrastructure; D003599:Cytoskeleton / Q000378:metabolism / Q000648:ultrastructure; D006801:Humans; D016169:Lymphocyte Function-Associated Antigen-1 / Q000378:metabolism / Q000648:ultrastructure*; D008214:Lymphocytes / Q000166:cytology* / Q000378:metabolism / Q000648:ultrastructure; D010703:Phorbol Esters / Q000494:pharmacology*
D002273:Carcinogens; D016169:Lymphocyte Function-Associated Antigen-1; D010703:Phorbol Esters