Subcellular localisation in the Prolyl OligoPeptidases — ASN Events
  1. Schedule
  2. Session Five - Poster Session A
  3. Subcellular localisation in the Prolyl OligoPeptidases

Subcellular localisation in the Prolyl OligoPeptidases (#123)

Hui Zhang 1 , Yiqian Chen 1 , Fiona M Keane 1 , Mark D Gorrell 1
  1. Centenary Institute, Newtown, NSW, Australia

Four prolyl oligopeptidase family members, including dipeptidyl peptidase 4 (DPP4), are cell-surface expressed whereas DPP8 and DPP9 have intracellular localizations. Precise DPP9 subcellular localization has not been reported. This study investigates the subcellular localisation of DPP9 and explores a potential role for DPP9 in focal adhesion.

Human full length DPP9 (wild-type DPP9) and enzyme inactive DPP9 (S729A) were cloned into an EGFP expression vector. Hela and Huh7 cells were transiently transfected and immunostained for markers for various organelles. Confocal microscopy showed diffuse DPP9 cytoplasmic staining. A high degree of co-localization was found between DPP9 and microtubules. Less co-localization was seen of DPP9 with Golgi and mitochondria. Enzyme inactive DPP9 showed a similar expression pattern as wild-type DPP9, indicating that enzyme activity does not affect subcellular distribution of DPP9. Live cell imaging of Huh7 cells indicated that DPP9 was present near the ruffling membrane of a moving cell. Upon simulation by PMA or Epidermal Growth Factor, DPP9 redistributed towards the ruffling membrane. These data indicate that DPP9 might have a role in membrane ruffling, which is important for cell spreading and migration.

To investigate whether DPP9 is a part of the focal adhesion complex, double labeling of DPP9 with different focal adhesion components was performed. Concentrated DPP9 was located on one side of the cell body, whereas on the opposite side more punctate DPP9 clustered at the cell edge. At the same edge, β1 integrins were enriched and were highly co-localized with DPP9. The same expression pattern was observed with DPP9 and talin. However, punctate DPP9 did not co-localize with vinculin. Therefore, DPP9 may be associated with the focal adhesion complex, possibly through binding to integrin and talin.

These data indicate that DPP9 localisation is consistent with microtubular transport and a role in cell adhesion and provide the first mechanistic insights into the role of DPP9 in cell adhesion and migration.