lab meeting 05/05/14

Jean-Ju Chung, Spatial Organization of CatSper in Sperm

  • (former collaborator of Sang-He)
  • Clapman lab
  • results now published, to appear soon.


  • ejaculated sperm not motile outside female environment. Hence ‘not fertile’.
  • what’s the difference? Bicarbonate rich, Albumin. pH changes sharply from 5 vagina to 8 in cervix / 9 in mouse fallopian tube.
  • consequent ‘capacitation’ of sperm cells. Go from activated motility, to hyperactivated (whip-like motion, believed to function in fusion)
  • sperm require few hours to mature.
  • CatSper — sperm specific Ca channel.


- Identified 4 channels in sperm.   
- knockouts are male-specific infertile
- lack hyper-active motility.  
- structurally more similar to K channel than other Ca / Na channels
- stay in the ER, don't become functional ion channels until mature sperm
- then localize in principle piece (main body of the tail).  
- Ca specific conductance abolished in any of the knockouts.  -- heterotetramer.
- progesterone activates human CatSper

How is CatSper organized?

  • Conventional imaging: CatSper is localized to the principle piece. Sometimes 2 lines, sometime 3 lines or apparent helix.
  • 9(doublet microtubules)+2(singlet) microtubule organization + 2 outer layers. ~300nm inner diameter
  • CatSper1 arranged in 4 long parallel lines in two double rows.
  • immunoEM see four doublets flanking each of the longitudinal columns.
  • CatSper is quadralateral before formation of the longitudal column in immature sperm.

How does this organization affect the function of beating?

  • CatSper colocalizes with Ca2+ signaling molecules like P-CaMKII, and PP2B-Ag
  • CatSper still organized in Caviolin knockout.
  • Caviolin not still organized in CatSper knockout.
  • functionally confines tyrosine phosphorylation to the interior of the axonneme – (microtubule bundle)
  • Maybe the clustering of CatSper is important to the signalling.

probing P-Tyr phosphorylation

  • add heavy labels to P-Tyr from Wt and CatSpe1 nulls
  • mix and mass-spec.
  • 62 phosphoylation sites on 45 proteins. (previously only 7 known)
  • 41 sites show 2 fold increase in P-tyr in the knockout.
  • find Src family kinases target CatSper-dependent phosphorylation pathways
  • Calmodulin (Ca binding) concentrated in center.
  • phosphorylated Calmodulin focused in the very center after capactiation, and focused on the perifery in the CatSper1 null.


  • Tyrosine phosphorylation is downstream of PKA in sperm.
  • upregulation of tyrosine phsophorylation in CatSper nulls is also PKA depedent.

relation to swimming

  • Capacitation generates heterogeneous sperm populations — different radial distributions of CatSper1
  • Motility correlative imaging.
    • all hyperactive swimming sperm have intact quadralateral structure of CatSper and focused concentration of pY.
  • use fluorescently labeled sperm to trace migration through female reproductive system in transgenic mice
  • CatSper null sperm don’t exit the uterus (or very few).
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