Molecular basis for CPAP-tubulin interaction in controlling centriolar and ciliary length

  • Nat Commun. 2016 Jun 16;7:11874. doi: 10.1038/ncomms11874.
Xiangdong Zheng  1  2  3 ,  Anand Ramani  4 ,  Komal Soni  5  6 ,  Marco Gottardo  7 ,  Shuangping Zheng  1  2 ,  Li Ming Gooi  4 ,  Wenjing Li  2  3 ,  Shan Feng  2  3 ,  Aruljothi Mariappan  4 ,  Arpit Wason  4 ,  Per Widlund  8 ,  Andrei Pozniakovsky  8 ,  Ina Poser  8 ,  Haiteng Deng  2 ,  Guangshuo Ou  2  3 ,  Maria Riparbelli  7 ,  Callaini Giuliano  7 ,  Anthony A Hyman  8 ,  Michael Sattler  5  6 ,  Jay Gopalakrishnan  4 ,  Haitao Li  1  2  9
Affiliations
  • 1. Beijing Advanced Innovation Center for Structural Biology, Department of Basic Medical Sciences, School of Medicine, Tsinghua University, Beijing 100084, China.
  • 2. MOE Key Laboratory of Protein Sciences, School of Life Sciences, Tsinghua University, Beijing 100084, China.
  • 3. Tsinghua-Peking Center for Life Sciences, Tsinghua University, Beijing 100084, China.
  • 4. Institute for Biochemistry I and Center for Molecular Medicine of the University of Cologne, Robert-Koch-Str. 21, Cologne 50931, Germany.
  • 5. Institute of Structural Biology, Helmholtz Zentrum München, Ingolstädter Landstr. 1, Neuherberg 85764, Germany.
  • 6. Biomolecular NMR at Center for Integrated Protein Science Munich and Department Chemie, Technische Universität München, Lichtenbergstr. 4, Garching 85747, Germany.
  • 7. Department of Life Sciences, University of Siena, Siena 53100, Italy.
  • 8. Max Planck Institute of Molecular Cell Biology and Genetics, Pfotenhauer Str. 108, Dresden 01307, Germany.
  • 9. Collaborative Innovation Center for Biotherapy, West China Hospital, Sichuan University, Chengdu 610041, China.
PMID: 27306797 DOI: 10.1038/ncomms11874
Abstract

Centrioles and cilia are microtubule-based structures, whose precise formation requires controlled cytoplasmic tubulin incorporation. How cytoplasmic tubulin is recognized for centriolar/ciliary-microtubule construction remains poorly understood. Centrosomal-P4.1-associated-protein (CPAP) binds tubulin via its PN2-3 domain. Here, we show that a C-terminal loop-helix in PN2-3 targets β-tubulin at the microtubule outer surface, while an N-terminal helical motif caps microtubule's α-β surface of β-tubulin. Through this, PN2-3 forms a high-affinity complex with GTP-tubulin, crucial for defining numbers and lengths of centriolar/ciliary-microtubules. Surprisingly, two distinct mutations in PN2-3 exhibit opposite effects on centriolar/ciliary-microtubule lengths. CPAP(F375A), with strongly reduced tubulin interaction, causes shorter centrioles and cilia exhibiting doublet- instead of triplet-microtubules. CPAP(EE343RR) that unmasks the β-tubulin polymerization surface displays slightly reduced tubulin-binding affinity inducing over-elongation of newly forming centriolar/ciliary-microtubules by enhanced dynamic release of its bound tubulin. Thus CPAP regulates delivery of its bound-tubulin to define the size of microtubule-based cellular structures using a 'clutch-like' mechanism.