Adenylate kinase 1 deficiency disrupts mouse sperm motility under conditions of energy stress†

Abstract

Mammalian spermatozoa are highly polarized cells characterized by compartmentalized cellular structures and energy metabolism. Adenylate kinase (AK), which interconverts two ADP molecules into stoichiometric amounts of ATP and AMP, plays a critical role in buffering adenine nucleotides throughout the tail to support flagellar motility. Yet the role of the major AK isoform, AK1, is still not well characterized. Here, by using a proteomic analysis of testis biopsy samples, we found that AK1 levels were significantly decreased in non-obstructive azoospermia (NOA) patients. This result was further verified by immunohistochemical staining of AK1 on a tissue microarray. AK1 was found to be expressed in post-meiotic round and elongated spermatids in mouse testis and subsequent mature sperm in the epididymis. We then generated Ak1 knockout mice, which showed that AK1 deficiency did not induce any defects in testis development, spermatogenesis or sperm morphology and motility under physiological conditions. We further investigated detergent-modeled epididymal sperm and included individual or mixed adenine nucleotides to mimic energy stress. When only ADP was available, Ak1 disruption largely compromised sperm motility, manifested as a smaller beating amplitude and higher beating frequency, which resulted in less effective forward swimming. The energy restriction/recover experiments with intact sperm further addressed this finding. Besides, decreased AK activity was observed in sperm of a male fertility disorder mouse model induced by cadmium chloride. These results cumulatively demonstrate that AK1 was dispensable for testis development, spermatogenesis or sperm motility under physiological conditions, but was required for sperm to maintain a constant adenylate energy charge to support sperm motility under conditions of energy stress.

Proteomic Profile of Sperm in Infertile Males Reveals Changes in Metabolic Pathways

“…YBX1, which is also known as Y-box transcription factor, is involved in spermatogenesis [15,16]. Mitochondrial ACO2 and AK1 are required for sperm motility [13,17]. Consistent with the proteomic 2; Supplementary Table 1), the upregulation of YBX1 and downregulation of ACO2 and AK1 in sperm from the ICSI group were experimentally validated (Fig.…”

Adenylate kinase 1 overexpression increases locomotor activity in medaka fish

“…In contrast, throughout the experiment at 15 °C, the locomotor activity of Ak1 -OE larvae did not differ from that of the WT larvae (Fig 3D). Several knockout studies have shown that Ak1 deficiency can be compensated for by other members of the Ak family under normal conditions, whereas Ak1 deficiency leads to failure of metabolic homeostasis under stress conditions [10,11,18]. As our behavioral assays were conducted without feeding, the lack of energy later in the experiment might have mimicked metabolic stress even at the moderate temperature of 25 °C, and this could have caused the large difference in activity between the Ak1 -OE and WT larvae on the last day of the assay.…”

“…15.460533 doi: bioRxiv preprint 3 (2ADP ↔ ATP + AMP) to maintain the adenine nucleotide balance and monitor energy consumption. Ak and its downstream adenine nucleotide signaling pathway have attracted attention because of their vital functions in many biological processes, such as the cell cycle, hormone secretion, and stress tolerance [5,[7][8][9][10][11]. To date, nine isoforms of AK (AK1-AK9) have been identified and well characterized in humans [6].…”

“…AK1 is the major isoform of AK and is expressed in the cytosol of most human tissues, with particularly high levels in the brain, the heart, skeletal muscles, and erythrocytes. Several reports have demonstrated the importance of Ak1 in metabolic stress conditions [9][10][11]. Interestingly, it was recently reported that hyperactive rat strains exhibit increased Ak1 expression [12].…”

Adenylate kinase 1 overexpression increases locomotor activity in medaka fish

“…Ak catalyzes the nucleotide phosphoryl exchange reaction (2ADP ↔ ATP + AMP) to maintain the adenine nucleotide balance and monitor energy consumption. Ak and its downstream adenine nucleotide signaling pathway have attracted attention because of their vital functions in many biological processes, such as the cell cycle, hormone secretion, and stress tolerance [ 5 , 7 – 11 ]. To date, nine isoforms of AK (AK1–AK9) have been identified and well characterized in humans [ 6 ] ( Fig 1A ).…”