Figure 7.
Conserved leucine residues outside the receptor interaction regions are required for iLIF activity. (A) Schematic representation of LIF-D and LIF-T cDNAs and the mutations introduced into these cDNAs. (B, i–iii) Anti-LIF immunostaining of Cos-1 cells 2 d after transfection with expression vectors for LIF-D (pmLIF-DX) (i), LIF-T (pmLIF-TX) (ii), and LIF-T L2I3-A (pmLIF-T L2I3-AX) (iii). All leucine mutants showed similar LIF staining to B, iii. (B, iv–vi) Confocal laser scanning images of a Cos-1 cell transfected with pmLIF L2I3-A GFP stained with Lysotracker lysosome and acidic vesicle stain. (iv) GFP; (v) Lysotracker; (vi) merged images. Bar, 10 μm. (C) Graphical representation of the percentage of LIF-staining Cos-1 cells exhibiting an apoptotic morphology 3 d after transfection with expression vectors directing expression of LIF-D, LIF-T, and mutated LIF-T cDNAs. (D) Graphical representation of β-galactosidase-positive cells 3 d after transfection with low-level expression vectors coupling expression of β-geo to no cDNA (pXIres), LIF-T (pmLIF-TIres), LIF-D (pmLIF-DXIres), LIF-T L2I3-A (pmLIF-T L2I3-AXIres), LIF-T L2-A (pmLIF-T L2-AXIres), LIF-T L4-A (pmLIF-T L4-AXIres), and LIF-T L5-A (pmLIF-T L5-AXIres). The number of staining cells is normalized to control transfections with the parental vector pXIres. Means and SDs were derived from three experiments.