Fig. 5. Ret autophosphorylation demonstrated by western blotting. (a) Autophosphorylation of c-Ret is barely detectable in the absence of GDNF (-), is strongly induced by 100 ng/ml GDNF (G), but not if cells are pre-treated with 0.1 U/ml heparinase III (G+H). Track H shows control cells treated with just heparitinase III but no GDNF. The bottom panel showing c-Ret regardless of phosphorylation state confirms equal loading of the samples. (b) Confirmation of GFR-1 expression by RET/GFR1-MDCK cells. RET/GFR1-MDCK cells express GFR-1, as expected, in addition to c-Ret (see b), and even normal MDCK cells express a little. The bottom panel, probed for MAP-kinase, is again a loading control.