title: A model of CatSper channel mediated calcium dynamics in mammalian spermatozoa.
abstract: CatSpers are calcium (Ca(2+)) channels that are located along the principal piece of mammalian sperm flagella and are directly linked to sperm motility and hyperactivation. It has been observed that Ca(2+) entry through CatSper channels triggers a tail to head Ca(2+) propagation in mouse sperm, as well as a sustained increase of Ca(2+) in the head. Here, we develop a mathematical model to investigate this propagation and sustained increase in the head. A 1-d reaction-diffusion model tracking intracellular Ca(2+) with flux terms for the CatSper channels, a leak flux, and plasma membrane Ca(2+) clearance mechanism is studied. Results of this simple model exhibit tail to head Ca(2+) propagation, but no sustained increase in the head. Therefore, in this model, a simple plasma membrane pump-leak system with diffusion in the cytosol cannot account for these experimentally observed results. It has been proposed that Ca(2+) influx from the CatSper channels induce additional Ca(2+) release from an internal store. We test this hypothesis by examining the possible role of Ca(2+) release from the redundant nuclear envelope (RNE), an inositol 1,4,5-trisphosphate (IP(3)) gated Ca(2+) store in the neck. The simple model is extended to include an equation for IP(3) synthesis, degradation, and diffusion, as well as flux terms for Ca(2+) in the RNE. When IP(3) and the RNE are accounted for, the results of the model exhibit a tail to head Ca(2+) propagation as well as a sustained increase of Ca(2+) in the head.
authors.affiliation: Mathematics Department, Tulane University, 6823 St. Charles Ave., New Orleans, LA 70118, USA. solson2@tulane.edu
authors.forename: Sarah D
authors.initials: SD
authors.lastname: Olson
authors.forename: Susan S
authors.initials: SS
authors.lastname: Suarez
authors.forename: Lisa J
authors.initials: LJ
authors.lastname: Fauci
mesh_terms: D000818:Animals; D002118:Calcium / Q000502:physiology*; D015220:Calcium Channels / Q000502:physiology*; D015544:Inositol 1,4,5-Trisphosphate / Q000502:physiology; D008297:Male; D051379:Mice; D008954:Models, Biological; D009685:Nuclear Envelope / Q000502:physiology; D013081:Sperm Motility / Q000502:physiology*; D013082:Sperm Tail / Q000502:physiology*; D013094:Spermatozoa / Q000502:physiology*
chemical_list: D015220:Calcium Channels; D015544:Inositol 1,4,5-Trisphosphate; D002118:Calcium