In addition, comparison of Sec15 localization with respect to Glu-tubulin (detyrosinated -tubulin, a marker of primary cilia) and -tubulin (a marker of basal bodies) further confirmed its ciliary localization

In addition, comparison of Sec15 localization with respect to Glu-tubulin (detyrosinated -tubulin, a marker of primary cilia) and -tubulin (a marker of basal bodies) further confirmed its ciliary localization. Open in a separate window FIGURE 4. Sec15 co-localizes with Rab8 in primary cilia. budding yeast exhibited that Sec2p (a Rabin8 homolog) interacts with GTP-Ypt32p (a Rab11 homolog), which, together with phosphatidylinositol 4-phosphate, Rifamdin recruits Sec2p to the test. For transfection, the genes of interest (isoforms are 5-AACAAGTGACGGATACTAATA-3 and 5-AAAGATATCATTCGATGTAGA-3. The control luciferase siRNA target sequence is usually 5-AACGTACGCGGAATACTTCGA-3. For siRNA treatment, cells were produced in DMEM and 10% FBS on coverslips. siRNA transfection was carried out in Opti-MEM with Oligofectamine (Invitrogen). The cells on coverslips were fixed 48C72 h after transfection. The remaining cells on plates were lysed for Western blot analysis. Antibodies Mouse anti-His6 antibody was purchased from Covance (Berkeley, CA). Rabbit anti-Rab11 antibody was from US Biological (Swampscott, MA). Mouse anti-c-Myc antibody 9E10 and rabbit anti-transferrin receptor antibody were from Santa Cruz Biotechnology (Santa Cruz, CA). Mouse anti-acetylated -tubulin monoclonal antibody and rabbit anti–tubulin polyclonal antibody were purchased from Sigma. Rabbit anti-Glu-tubulin antibody was purchased from Millipore (Billerica, MA). Secondary antibodies labeled with Alexa Fluor 488 or Alexa Fluor 594 for immunofluorescence were purchased from Invitrogen. Recombinant Protein Expression and in Vitro Binding Assays The NusA-His6-Rab8a fusion protein was expressed in the pET43 vector as described previously (31, 32). The NusA-His6-Rab8a fusion protein was purified from bacteria with TALON metal affinity resin (Clontech). The generation of Rabin8 fusion proteins was as described previously (10). GST fusion proteins were expressed in pGEX vectors in bacteria and purified using glutathione-Sepharose 4B. The beads were then washed four occasions with binding buffer (20 mm Tris-HCl (pH 7.4), 100 mm NaCl, 1 mm EDTA, 1 mm DTT, 10 mm MgCl2, and 1% Triton X-100) and used directly for binding assays. Sec15 was expressed in the presence of [35S]methionine using a TnT Quick kit (Promega). The translation products were then incubated with protein-coupled glutathione-Sepharose beads in binding buffer Rifamdin for 1.5 h at room temperature. After washing four occasions with binding buffer, the bound proteins were separated by 10% SDS-PAGE. The gels were dried, and the protein bands were visualized by phosphorimaging. To examine the conversation between Rabin8 and Rab11, His6-Rab11a was expressed in pET32a. The purified proteins were dialyzed overnight with 20 mm Tris-HCl (pH 7.4), 100 mm NaCl, and 1 mm DTT. Purified Rab11a was incubated with GST-Rabin8 immobilized on glutathione-Sepharose in binding buffer made up of GTPS for 2.5 h at 4 C. After four washes with binding buffer, bound Rab11 was analyzed by SDS-PAGE and Western blotting using antibodies against the His6 epitope. The binding of GST-Rab8 fusion proteins to translated Rabin8 or Rabin8(300C305) was carried out under the same conditions as described above except that Rab8 was preloaded with 50 m GDPS. GEF Activity Assays Rab8 was cleaved from the NusA-His6-Rab8a fusion protein using thrombin. GST-Rabin8 and GST-Rabin8(300C305) were expressed and purified as described above, and GST was removed using thrombin. The GEF activity of Rabin8 or Rabin8(300C305) toward Rab8 was decided as previously described (10). Data were statistically analyzed using Student’s test (= 3). Immunofluorescence Microscopy For Sec15, Rab11, and transferrin receptor staining, cells were fixed with 4% paraformaldehyde in PBS for 5 min at 37 C and then permeabilized with 0.2% Triton X-100 in PBS. For cilium staining, cells were fixed with 4% paraformaldehyde in PBS for 5 min, followed by fixation with ice-cold Rabbit Polyclonal to DLGP1 methanol for 3 min. The cells were then permeabilized Rifamdin with 1% Triton X-100 in PBS for 10 min, blocked in PBS with 3% BSA, and incubated sequentially with primary and secondary antibodies. RESULTS Rabin8 Interacts with Sec15 Rifamdin In yeast, Sec15p was shown to interact with Sec2p, the GEF for the Rab protein Sec4p involved in exocytosis (33). Here, we examined the conversation between human Sec15 and Rabin8. GST-Rabin8 fusions with serial deletions at the C terminus were constructed (Fig. 1translated [35S]-methionine-labeled Sec15 or NusA-His6-tagged Rab11a. Sec15 interacted with a Rabin8 fragment lacking the C-terminal 130 amino acids; full-length Rabin8 (amino acids 1C460) and Rabin8 (amino acids 1C400) had much weaker interactions with Sec15 (Fig. 1indicate the amino acid sequences. indicate the GEF domain name (amino acid 84C255). in the presence of [35S]methionine (Rab11 and Ypt32p) through their C-terminal halves, we compared the sequences of Rabin8 and Sec2p located C-terminal to their GEF domains (Fig. 2for binding was.