A novel epididymal quiescence factor inhibits sperm motility by modulating NOS activity and intracellular NO‐cGMP pathway. Issue 5 (2nd January 2018)

• Record Type: Journal Article
• Authors: Ghosh, Prasanta; Mukherjee, Sandipan; Bhoumik, Arpita; Dungdung, Sandhya R.
• Is Part Of: Journal of cellular physiology. Volume 233:Issue 5(2018:May)
• Page Start: 4345
• Page End: 4359
• Publication Date: 2018-01-02
• Subjects: epididymal plasma -- nitric oxide synthase -- NO‐cGMP pathway -- protein purification -- sperm quiescence; Physiology -- Periodicals; Cell physiology -- Periodicals; 571.6
• DOI: 10.1002/jcp.26275
• Languages: English
• ISSNs: 0021-9541

Abstract

Abstract : Mature and potentially motile spermatozoa stored in cauda epididymis in an inactive state for approximately 30 days; however, during ejaculation they regain motility. To understand the actual molecular mechanism of the sperm quiescence during caudal stay, a proteinaceous quiescence factor (QF) has been purified from caprine epididymal plasma to apparent homogeneity. In the present study complete purification, detailed characterization as well as mechanistic pathway of QF has been described. QF is purified to 215‐fold with 45% activity recovery. It is a 59 kDa monomeric protein with isoelectric point 5.8 and optimally active at pH 7.5. Circular dichroism spectroscopy and atomic force microscopy study confirm its α‐helical secondary structure and globular tertiary conformation. QF is a thermo‐stable protein as higher temperature does not alter its helical structure. N‐terminal amino acid sequencing and MALDI analysis of QF did not find 100% similarity with any available protein of the database, proved its novelty. QF at 2 μM dose inhibits sperm progressive forward motility within 10 min. This motility inhibitory activity of QF is mediated by reducing NOS enzyme activity and subsequently decreasing the intracellular NO and cGMP concentration. It does not modulate intracellular Ca ++ and cAMP concentration. QF has no adverse effect on DNA integrity and morphology of spermatozoa. Motility inhibitory action of QF is reversible. Thus, the role of QF in maintaining energy saving quiescence state of mature cauda spermatozoa and its reactive nitrogen species reducing activity may lead to a new direction for storage of spermatozoa and idiopathic male infertility. Abstract : Newly identified 59 kDa monomeric quiescence factor (QF) is an α‐helical globular protein which inhibits sperm progressive forward motility by decreasing NOS enzyme activity and subsequently reducing intracellular NO‐cGMP concentration without modulating intracellular Ca ++ and cAMP concentration. QF does not damage spermatozoa and its motility inhibitory efficacy is reversible. This study reveals the quiescence mechanism of mature spermatozoa and its energy saving strategy during storage and may help in understanding motility related idiopathic male infertility.