COMMUNICATION - INTRACELLULAR PRECURSOR INTERLEUKIN (IL)-1-ALPHA, BUTNOT MATURE IL-1-ALPHA, IS ABLE TO REGULATE HUMAN ENDOTHELIAL-CELL MIGRATION IN-VITRO

The human umbilical vein endothelial cell (HUVEC) has a finite lifespa n in vitro, and senescent HUVEC contain elevated levels of the negativ e growth regulator interleukin (IL)-1 alpha, IL-1 alpha is translated as a signal peptide sequence-less cytosolic 31-kDa precursor (IL-1 alp ha p), which undergoes proteolytic activation to release the mature ca rboxyl terminus 17-kDa protein (IL-1 alpha m), Both the IL-1 alpha p a nd IL-1 alpha m proteins are biologically active as exogenous cytokine s. Interestingly, only IL-1 alpha p contains a nuclear localization se quence between residues 79 and 85, To further study the role of intrac ellular IL-1 alpha in the regulation of human endothelial cell functio n, a spontaneous HUVEC transformant was stably transfected with IL-1 a lpha p, IL-1 alpha m, and the IL-1 alpha p K82N mutant, which attenuat es the nuclear traffic of IL-1 alpha p, Interestingly, the IL-1 alpha p transfectants were found to have a lower migratory potential than ei ther IL-1 alpha m or IL-1 alpha p K82N transfectants, and the addition of the IL-1 receptor antagonist did not alter the migration of these cells. Immunofluorescence microscopy demonstrated that only the IL-1 a lpha p transfectants exhibited prominent staining for beta-catenin-ass ociated cell-to-cell contacts, as well as pronounced vimentin intermed iate filaments and actin cytoskeleton staining, These data suggest tha t IL-1 alpha p, and not IL-1 alpha m, may function as an intracellular regulator of the migratory capacity of the human endothelial cell and that the nuclear localization sequence present within IL-1 alpha p ma y be involved in regulating this function.