Fig. 1

The C-terminal region of CD44 variant 3 binds to TrkA. A Schematic representation of the CD44 gene and protein structure. Alternative splicing leads to the expression of CD44 variants, thus the insertion of exon 8 leads to the expression of a CD44 protein containing variant 3 (CD44v3) and the insertion of exon 11 leads to the expression of a CD44 containing variant 6 (CD44v6) (B) TrkA/CD44v3 complex formation in COS-7 cells expressing TrkA and CD44v3 was detected by the proximity ligation assay (PLA), which was performed 0, 5 and 30 min after the initiation of NGF (100 ng/ml) treatment. The images represent signals detected by PLA. Quantification of the red spots was performed by ImageJ software (30 randomly chosen fields per condition of three different experiments). Statistical analyses were performed using one-way ANOVA followed by Bonferroni’s posttest. Error bars represent the standard error of the mean (S.E.M.); *** p < 0.001. ns, nonsignificant. C NGF and/or TrkA binding to CD44v3 was measured by microscale thermophoresis (MST). MST experiments were performed on whole cell extracts of COS-7 cells expressing CD44v3. D, E Modeling of TrkA and CD44 variant exon 3; sequence alignment of TrkA isoforms (F) or TrkA, TrkB and TrkC (G) using the Clustal Omega program. H Structure of histidine, leucine and arginine amino acids (ChemSketch software). I Modeling of TrkA H112A and CD44v3