Int. J. Dev. Biol. 52: 615 - 626 (2008)

https://doi.org/10.1387/ijdb.072535kb

Vol 52, Issue 5-6

Special Issue: Fertilization

Mobilisation of stored calcium in the neck region of human sperm - a mechanism for regulation of flagellar activity

Published: 1 July 2008

Kweku Bedu-Addo¹, Sarah Costello², Claire Harper³, Gisela Machado-Oliveira², Linda Lefievre⁴, Christopher Ford⁴, Christopher Barratt⁵ and Stephen Publicover^2,*

¹Kwame Nkrumah University of Science and Technology, Kumasi, Ghana, ²School of Biosciences, University of Birmingham, UK ³School of Biological Sciences, University of Liverpool, UK, ⁴Department of Medicine, University of Birmingham, UK and ⁵Medical School, Ninewells Hospital, Dundee, UK

Abstract

Calcium signalling plays a pivotal role in sperm physiology, being intimately involved in the regulation of acrosome reaction, chemotaxis and hyperactivation. Here we describe briefly the mechanisms of calcium regulation in somatic cells and the ways in which these mechanisms have been adapted to function in mature spermatozoa. We then consider recent data from this and other laboratories on the responses of sperm to three compounds: progesterone and nitric oxide (both products of the cumulus oophorus) and 4-aminopyridine. All of these compounds induce calcium signals in the posterior sperm head and neck region and, when applied at appropriate concentrations, modify flagellar activity, causing asymmetric bending of the proximal flagellum. We argue that these effects reflect a common mode of action, mobilisation of calcium stored in the sperm neck region. Finally we consider the nature of calcium signalling pathways in sperm. We suggest that this highly specialised and extremely polarised cell, though working with the same calcium signalling 'tools' as those of somatic cells, employs them to generate unusually 'hard-wired' calcium signals that do not act to integrate stimuli. 'Leakage' between these calcium signalling pathways will generate inappropriate responses, compromising functioning of the cell.

Keywords

sperm, calcium, nitric oxide, calcium store, hyperactivation