DENND4 family proteins are specific GEFs for Rab10. (A) A representative panel of human Rab proteins was tested against 10 nM of human DENND4B expressed as a FLAG-tagged protein in HeLa cells using the GDP-releasing assay. (B) Human DENND4A, DENND4B, and DENND4C were tested against a subset of Rab10-related Rabs using the GTP-binding assay. Again, 10 nM of each FLAG-tagged DENN protein purified from HeLa cells was used for these assays. Error bars show the standard error of the mean. The red line marks double the median value. (C and D) A representative panel of human Rab proteins was tested against 10 nM of His6-tagged human Rabin3/Rabin8 (C) and Rabin3-like/GRAB purified from bacteria using the GDP-releasing assay (D). Error bars indicate standard error of the mean. (E) HeLa cells expressing EGFP-tagged DENND4B were transfected with mCherry-tagged Rab10, or stained for the markers indicated. 4× enlargements of the Rab10-positive tubules are shown in the top panels. Bar, 10 µm.
