CSPP is a ciliary protein interacting with Nephrocystin 8 and required for cilia formation.
We described previously the cell cycle- and microtubule-related functions of two splice isoforms of the centrosome spindle pole-associated protein (CSPP and CSPP-L). Here, we show that endogenous CSPP isoforms not only localize to centrosomes and the midbody in cycling cells but also extend to the cilia axoneme in postmitotic resting cells. They are required for ciliogenesis in hTERT-RPE1 cells in vitro and are expressed in ciliated renal, retinal, and respiratory cells in vivo. We report that CSPP isoforms require their common C-terminal domain to interact with Nephrocystin 8 (NPHP8/RPGRIP1L) and to form a ternary complex with NPHP8 and NPHP4. We find CSPP-L to be required for the efficient localization of NPHP8 but not NPHP4 to the basal body. The ciliogenesis defect in hTERT-RPE1 cells is, however, not mediated through loss of NPHP8. Similar to the effects of ectopical expression of CSPP-L, cilia length increased in NPHP8-depleted cells. Our results thus suggest that CSPP proteins may be involved in further cytoskeletal organization of the basal body and its primary cilium. To conclude, we have identified a novel, nonmitotic function of CSPP proteins placing them into a ciliary protein network crucial for normal renal and retinal tissue architecture and physiology.
Department of Radiation Biology, Institute for Cancer Research, The Norwegian Radium Hospital, N-0310 Oslo, Norway. sebastip@rr-research.no
Sebastian
S
Patzke
Sambra
S
Redick
Abdirashid
A
Warsame
Carlos A
CA
Murga-Zamalloa
Hemant
H
Khanna
Stephen
S
Doxsey
Trond
T
Stokke
D048868:Adaptor Proteins, Signal Transducing / Q000378:metabolism*; D000918:Antibody Specificity; D054468:Axoneme / Q000378:metabolism; D001980:Bronchi / Q000166:cytology / Q000378:metabolism; D002453:Cell Cycle; D018797:Cell Cycle Proteins / Q000378:metabolism*; D002460:Cell Line; D002502:Centrioles / Q000378:metabolism; D002923:Cilia / Q000378:metabolism*; D004847:Epithelial Cells / Q000166:cytology / Q000378:metabolism; D055785:Gene Knockdown Techniques; D006801:Humans; D007668:Kidney / Q000166:cytology / Q000378:metabolism; D008869:Microtubule-Associated Proteins / Q000378:metabolism*; D038081:Organogenesis; D011485:Protein Binding; D020033:Protein Isoforms / Q000378:metabolism; D055550:Protein Stability; D021381:Protein Transport; D012160:Retina / Q000166:cytology / Q000378:metabolism
D048868:Adaptor Proteins, Signal Transducing; C514207:CSPP1 protein, human; D018797:Cell Cycle Proteins; D008869:Microtubule-Associated Proteins; D020033:Protein Isoforms; C532826:RPGRIP1L protein, human