Role of Intracellular Divalent Cations on the Adenylate Cyclase Activation by Human LH in mLTC-1 Leydig Cells

Nguyen, Thi Mong Diep; Tran, Van Giang; Nguyen, Thi Chi Hieu; Nguyen, Ba Nghi

doi:10.30491/jabr.2021.286454.1382

Role of Intracellular Divalent Cations on the Adenylate Cyclase Activation by Human LH in mLTC-1 Leydig Cells

Document Type : Original Article

Authors

Thi Mong Diep Nguyen ¹

Van Giang Tran ²

Thi Chi Hieu Nguyen ³

Ba Nghi Nguyen ³

¹ Department of Applied Biology & Agriculture, Faculty of Natural Sciences, Quy Nhon University, Binh Dinh 820000, Vietnam

² Faculty of Biology, Hue University of Education, Hue University, Hue 530000, Vietnam

³ Faculty of Applied Biology, Quang Trung University, Quy Nhon, Vietnam

10.30491/jabr.2021.286454.1382

Abstract

Introduction: The Luteinizing Hormone (LH) regulates Leydig cell activities through LHR occupation, promoting Gs protein and/or β-arrestin activation. The activated GsαGTP subunit stimulates Adenylyl Cyclase (ACs) and, therefore, intracellular cyclic Adenosine Monophosphate (cAMP) accumulation from the AC substrate Adenosine Triphosphate (ATP). The divalent cations, magnesium (Mg²⁺) or manganese (Mn²⁺) associate with ATP to form the real substrates of ACs. In addition, ACs are sensitive to calcium (Ca²⁺) but in a different way than Mg²⁺ or Mn²⁺. Indeed, LH increases the cytoplasmic calcium ion concentration ([Ca²⁺]cyt) but only when Ca²⁺ is present in the extracellular medium.
Materials and Methods: In the present study, the effects of intracytoplasmic Ca²⁺, Mg²⁺, and Mn²⁺ on the cyclic AMP response to human LH in mLTC-1 Leydig tumor cells were investigated. The mLTC-1 cells were incubated at 37 °C in media supplemented with and without 5 µM Ca²⁺, 5 µM Mg²⁺, or 5 µM Mn²⁺. The intracellular cyclic AMP accumulation was then monitored under LH stimulation.
Results: Our findings revealed that only Mg²⁺ and Mn²⁺ in the extracellular medium potentiate the cAMP response to hLH, in contrast to Ca²⁺. In addition, we also showed that HCO3- increased the stimulation of the adenylyl cyclase enzyme by Ca²⁺, Mg²⁺ or Mn²⁺.
Conclusions: In mLTC-1 cells, extracellular Mg²⁺ and Mn²⁺ might potentiate LH-stimulated ACs activity by favoring LH interaction with its receptor, whereas Ca²⁺ from internal stores might be mobilized towards the cytoplasm to increase ACs activity, possibly through the soluble isoform.

Keywords

Adenosine Monophosphate

Adenylyl Cyclase, mLTC-1

Luteinizing Hormone

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