LSP1 modulates the locomotion of monocyte-differentiated U937 cells

To examine the effect of lymphocyte specific protein 1 (LSP1) on phagocytic cell motility, stable transfection of LSP1-null U937 cell line with an epi somal expression vector carrying the LSP1 complementary DNA created lines e xpressing varied LSP1 levels. Mock transfectants without LSP1 (U937(-)) end cell lines with LSP1 levels similar to those of monocytes (U937(+)) or 4-f old those of monocytes (U937(++++)) express LSP1 as indicated and express o ther actin-binding proteins at normal levels before or after monocytic indu ction (MI) with dibutyryl cyclic adenosine monophosphate. The cell lines we re compared for rate of growth and cell division and, after monocytic diffe rentiation, were video-tracked to measure locomotion as distance moved in 2 hours and examined for morphologic changes. Rates of cell division and gro wth were similar for different U937 cell lines at all LSP1 levels. In contr ast, mean rate of locomotion (micrometers moved in 2 hours) was slower in M I-U937(++++) (7.78+1.11 mu m, n = 3) and MI-U937(-) (23.89 + 2.78 mu m, n = 3) than in MI-U937(+) cells (50.77 + 4.11 mu m, n = 3), Compared with MI-U 937(-), the locomotive histogram (n = 150 cells) of MI-U937(+) or MI-U937(+++) cells shows all cells move respectively faster or slower as an entire cell population. In LSP1(+) U937 phagocytes, high LSP1 levels inhibit some (locomotion) but not ail (cytokinesis) cell motile behaviors and cause the formation of surface projections, In contrast, normal LSP1 levels in U937 p hagocytes enhance some (locomotion) but not all (cytokinesis) cellular moti le behaviors and have no effect on cell morphology, Therefore, LSP1 level h as a unique biphasic effect on cellular locomotion, The data suggest LSPI i s an important regulator of phagocyte locomotion, (C) 2000 by The American Society of Hematology.