Dissecting the axoneme interactome: the mammalian orthologue of Chlamydomonas PF6 interacts with sperm-associated antigen 6, the mammalian orthologue of Chlamydomonas PF16.
The axoneme central apparatus is thought to control flagellar/ciliary waveform and maintain the structural integrity of the axoneme, but proteins involved in these processes have not been fully elucidated. Moreover the network of interactions among them that allows these events to take place in a compact space has not been defined. PF6, a component of the Chlamydomonas central apparatus, is localized to the 1a projection of the C1 microtubule. Mutations in the Chlamydomonas PF6 gene result in flagellar paralysis. We characterized human and murine orthologues of PF6. The murine Pf6 gene is expressed in a pattern consistent with a role in flagella and cilia, and the PF6 protein is indeed localized to the central apparatus of the sperm flagellar axoneme. We discovered that a portion of PF6 associates with the mammalian orthologue of Chlamydomonas PF16 (sperm-associated antigen 6 (SPAG6)), another central apparatus protein that is localized to the C1 microtubule in algae. A fragment of PF6 corresponding to the PF6 domain that interacts with SPAG6 in yeast two-hybrid assays and colocalizes with SPAG6 in transfected cells was missing from epididymal sperm of SPAG6-deficient mice. SPAG6 binds to the mammalian orthologue of PF20, which in Chlamydomonas is located in bridges connecting the C2 and C1 microtubules. Thus, PF6, SPAG6, and PF20 form a newly identified network that links together components of the axoneme central apparatus and presumably participates in its dynamic regulation of ciliary and flagellar beat.
Zhang
Zhibing
Z
Center for Research on Reproduction and Women's Health and the Department of Ophthalmology, University of Pennsylvania Medical Center, Philadelphia, Pennsylvania 19104, USA.
Jones
Brian H
BH
Tang
Waixing
W
Moss
Stuart B
SB
Wei
Zhangyong
Z
Ho
Clement
C
Pollack
Michael
M
Horowitz
Eran
E
Bennett
Jean
J
Baker
Michael E
ME
Strauss
Jerome F
JF
D020418:Algal Proteins / Q000235:genetics*; D000595:Amino Acid Sequence; D000818:Animals; D016466:CHO Cells; D016825:Chlamydomonas reinhardtii / Q000235:genetics; D002923:Cilia / Q000378:metabolism; D006224:Cricetinae; D003412:Cricetulus; D005407:Flagella / Q000378:metabolism; D006801:Humans; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D008868:Microtubule Proteins / Q000096:biosynthesis* / Q000235:genetics; D008869:Microtubule-Associated Proteins / Q000096:biosynthesis* / Q000235:genetics*; D008969:Molecular Sequence Data; D009154:Mutation; D015800:Protozoan Proteins / Q000235:genetics*; D017386:Sequence Homology, Amino Acid; D013094:Spermatozoa / Q000378:metabolism*; D020798:Two-Hybrid System Techniques
D020418:Algal Proteins; D008868:Microtubule Proteins; D008869:Microtubule-Associated Proteins; C107014:PF20 protein, Chlamydomonas; C504273:PF6 protein, mouse; D015800:Protozoan Proteins; C400106:SPAG6 protein, human