Centrin is a conserved component of centrioles in animals and basal
Centrin is a conserved component of centrioles in animals and basal bodies in flagellated organisms. Several distinct protein bands were detected (Fig. 3B). The biggest protein band exhibited a molecular mass way over 250 kDa (Fig. 3B), and LC-MS/MS showed that this band represented Tb927.7.920, which encodes a putative inner-arm dynein with a predicted molecular mass of 465 kDa and is one of the two IAD5-family dyneins that share an overall sequence identify of 33.2%18. We named this dynein TbIAD5-1. The other protein bands between 50C150 kDa were degradation products of TbIAD5-1. Figure TCN 201 manufacture 3 TbCentrin3 associates with TbIAD5-1, an inner-arm dynein heavy chain Figure 6 Effect of TbIAD5-1 knockdown on the localization and stability of TbCentrin3 To confirm the interaction between TbCentrin3 and TbIAD5-1, we carried out co-immunoprecipitation. Endogenously PTP-tagged TbCentrin3 and triple HA-tagged TbIAD5-1 were co-expressed in the same cell line. Immunoprecipitation of TbCentrin3::PTP was capable of pulling down TbIAD5-1::3HA from the cell lysate prepared by sonication (Fig. 3C). Reciprocal immunoprecipitation with anti-HA antibody for precipitation of TbIAD5-1::3HA was also able to pull down TbCentrin3::PTP from trypanosome cell lysate (Fig. 3D). These results further confirm that TbCentrin3 indeed interacts with TbIAD5-1 and suggest that TbCentrin3 is a component of an inner-arm dynein complex in trypanosomes. To determine the subcellular localization of TbIAD5-1 as well as to examine whether it co-localizes with TbCentrin3, we tagged the endogenous TbIAD5-1 with a C-terminal triple HA epitope in the procyclic cell line expressing endogenously EYFP-tagged TbCentrin3. In all the cells examined, TbIAD5-1::3HA was found in the flagellum throughout the cell cycle and co-localized with TbCentrin3::EYFP (Fig. 3E and data not shown). Given that TbCentrin3 and TbIAD5-1 interact (Fig. 3BCD), these observations suggest that the two proteins form a complex in the flagellum. TbIAD5-1 RNAi leads to motility defect in the procyclic form To investigate the function of TbIAD5-1, TCN 201 manufacture RNAi was carried out in the procyclic form. After RNAi induction for 2 days, TbIAD5-1 mRNA was decreased to about 30% of that in the non-induced control cells as measured by quantitative RT-PCR (Fig. 4A). The protein level of TbIAD5-1, which was endogenously Rabbit Polyclonal to C-RAF (phospho-Ser301) tagged with a triple HA epitope, was gradually decreased from the first day of RNAi induction and reached the lowest level after 3 days of RNAi, but the protein was not completely depleted (Fig. 4B). This significant down-regulation of TbIAD5-1 in the procyclic form only slightly slowed down cell growth (Fig. 4C), similar to the growth defect of TbCentrin3 RNAi cells (Fig. 2C). Like TbCentrin3 RNAi, TbIAD5-1 RNAi also caused severe defect in cell motility as demonstrated by sedimentation assay (Fig. 4D), motility tracing (Fig. 4E, F), and time-lapse video microscopy (Supplementary Movie 3). Although the flagella of the TbIAD5-1 RNAi cells were still capable of beating, the RNAi cells apparently lost directional motility and, instead, were just spinning and tumbling, remaining primarily at one location, or only traveled a short distance (Fig. 4E, F and Supplementary Movie 3). In contrast, the non-induced control cells were able to travel a long distance in a short time under the same experimental conditions (Fig. 4E, F and Supplementary Movie 4). The motility defect caused by TbIAD5-1 RNAi was very similar to that caused by TbCentrin3 RNAi. Given that the two proteins interact in the flagellum (Fig. 3), TbCentrin3 apparently plays an essential role in the TbIAD5-1 complex. Number 4 RNAi of TbIAD5-1 in the procyclic form causes problems in cell motility TbCentrin3 is definitely required for assembly TCN 201 manufacture of TbIAD5-1 We tested whether TbCentrin3 knockdown affects the localization of TbIAD5-1 to the flagellum. Immunostaining of paraformaldehyde-fixed.