Infertility constitutes a global medical problem, with male infertility contributing to half of all cases. Moreover, more than 70% of male infertility cass are considered idiopathic. This huge gap in our understanding of etiology of male infertility is partially attributed to our insufficient knowledge of physiology of spermatozoa, and human sperm cells in particular. While delicate regulation of sperm physiology occurs on many levels, its regulation by bioactive lipids deserves special attention. Our preliminary data indicate that several bioactive lipids influence the activity of sperm ion channels, which in turn regulate sperm motility and the acrosome reaction. For example, the steroid hormone progesterone stimulate the opening of the primary calcium channel of human sperm, CatSper, and controls sperm intracellular Ca2+. Progesterone also inhibits potassium sperm channel KSper. Our preliminary data indicate that CatSper channel can be inhibited by certain fatty acids, but also in addition to progesterone, can be up-regulated by an unknown sperm endogenous lipid easily extracted by fatty acid free bovine serum albumin (faf BSA) and -cyclodextrin. A brief incubation of sperm with either faf BSA or -cyclodextrin results in inhibition of CatSper activity. These experiments were done under conditions when sperm cytoplasm is removed, but sperm membrane stays intact. Moreover, such action is reversible indicating that the molecule responsible for activation of CatSper can be synthesized by intact sperm plasma membrane in the absence of secondary messengers. In addition, our recently published data indicate that many sperm ion channels and the molecules that modulate their activity are specific to human spermatozoa, and either are not observed, or their functions are altered in murine spermatozoa. This highlights the necessity to concentrate efforts of this proposal on studying bioactive lipid signaling in human spermatozoa specifically. In order to identify the molecule(s) responsible for sensitizing CatSper channel we will perform lipid extraction from human sperm plasma membrane by -cyclodextrin in order to deplete them from CatSper sensitizer, wait for the later to recover, and again extract lipids with -cyclodextrin. The newly synthesized lipids will be identified and tested for their ability to modulate CatSper. We will also obtain bioactive profiling of human ejaculated and capacitated spermatozoa. The knowledge gained from the proposed research will fill in gaps in our understanding of the basic mechanisms underlying the regulation of human sperm by bioactive lipids, may lead to the development of novel diagnostic tests for male infertility, and to the development of male contraceptives.

Public Health Relevance

This proposal aimed to reveal new molecular mechanisms by which bioactive lipids regulate sperm calcium channel CatSper and hence impact mammalian sperm physiology. The results obtained from the proposed research will help define our understanding of these fundamental mechanisms, may lead to improved diagnostic and treatment of male infertility, and provide new targets for male contraception.

Agency
National Institute of Health (NIH)
Institute
Eunice Kennedy Shriver National Institute of Child Health & Human Development (NICHD)
Type
Exploratory/Developmental Grants (R21)
Project #
5R21HD081403-02
Application #
9020246
Study Section
Cellular, Molecular and Integrative Reproduction Study Section (CMIR)
Program Officer
Moss, Stuart B
Project Start
2015-03-01
Project End
2017-02-28
Budget Start
2016-03-01
Budget End
2017-02-28
Support Year
2
Fiscal Year
2016
Total Cost
Indirect Cost
Name
University of California Berkeley
Department
Biochemistry
Type
Schools of Arts and Sciences
DUNS #
124726725
City
Berkeley
State
CA
Country
United States
Zip Code
94704
Mannowetz, Nadja; Mundt, Nadine; Lishko, Polina V (2018) Reply to Brenker et al.: The plant triterpenoid pristimerin inhibits calcium influx into human spermatozoa via CatSper. Proc Natl Acad Sci U S A 115:E347-E348
Lishko, Polina V; Mannowetz, Nadja (2018) CatSper: A Unique Calcium Channel of the Sperm Flagellum. Curr Opin Physiol 2:109-113
Miller, Melissa R; Kenny, Samuel J; Mannowetz, Nadja et al. (2018) Asymmetrically Positioned Flagellar Control Units Regulate Human Sperm Rotation. Cell Rep 24:2606-2613
Mannowetz, Nadja; Miller, Melissa R; Lishko, Polina V (2017) Regulation of the sperm calcium channel CatSper by endogenous steroids and plant triterpenoids. Proc Natl Acad Sci U S A 114:5743-5748
Miller, Melissa R; Mannowetz, Nadja; Iavarone, Anthony T et al. (2016) Unconventional endocannabinoid signaling governs sperm activation via the sex hormone progesterone. Science 352:555-9
Syeda, Shameem Sultana; Carlson, Erick J; Miller, Melissa R et al. (2016) The Fungal Sexual Pheromone Sirenin Activates the Human CatSper Channel Complex. ACS Chem Biol 11:452-9
Lishko, Polina V (2016) Contraception: Search for an Ideal Unisex Mechanism by Targeting Ion Channels. Trends Biochem Sci 41:816-818
Brown, Sean G; Publicover, Stephen J; Mansell, Steven A et al. (2016) Depolarization of sperm membrane potential is a common feature of men with subfertility and is associated with low fertilization rate at IVF. Hum Reprod 31:1147-57
Björkgren, Ida; Lishko, Polina V (2016) Purinergic signaling in testes revealed. J Gen Physiol 148:207-11
Lishko, Polina; Kirichok, Yuriy (2015) Signaling the differences between cilia. Elife 4: