Autophagy-related proteins are functionally active in human spermatozoa and may be involved in the regulation of cell survival and motility

Abstract

Macroautophagy (hereafter autophagy) is an evolutionarily highly conserved cellular process that participates in the maintenance of intracellular homeostasis through the degradation of most long-lived proteins and entire organelles. Autophagy participates in some reproductive events; however, there are not reports regarding the role of autophagy in the regulation of sperm physiology. Hence, the aim of this study was to investigate whether autophagy-related proteins are present and functionally active in human spermatozoa. Proteins related to autophagy/mitophagy process (LC3, Atg5, Atg16, Beclin 1, p62, m-TOR, AMPKα 1/2, and PINK1) were present in human spermatozoa. LC3 colocalized with p62 in the middle piece of the spermatozoa. Autophagy activation induced a significant increase in motility and a decrease in PINK1, TOM20 expression and caspase 3/7 activation. In contrast, autophagy inhibition resulted in decreased motility, viability, ATP and intracellular calcium concentration whereas PINK1, TOM20 expression, AMPK phosphorylation and caspase 3/7 activation were significantly increased. In conclusion our results show that autophagy related proteins and upstream regulators are present and functional in human spermatozoa. Modification of mitochondrial proteins expression after autophagy activation/inhibition may be indicating that a specialized form of autophagy named mitophagy may be regulating sperm function such as motility and viability and may be cooperating with apoptosis.

The mitochondria-targeted antioxidant MitoQ ameliorated tubular injury mediated by mitophagy in diabetic kidney disease via Nrf2/PINK1

“…TOM20 and VDAC are mitochondrial member proteins. TOM20 quantification is widely performed to monitor mitochondrial mass during mitophagy, [31] and VDAC1 degradation by ubiquitination is associated with mitophagy. [32] IHC revealed notably decreased TOM20 expression in the tubules of db/db mice compared to those of controls, and mitoQ treatment reversed this change (Fig.…”

“…[21], [42], [43] In this study, we used the mitochondria-targeted antioxidant mitoQ to overcome this limitation. [21], [31] Pre-treatment with mitoQ alleviated tubular damage in db/db mice, a change reflected by deceases in the levels of tubular injury markers, such as β-NAG. Notably, mitochondrial oxidative stress, mitochondrial fragmentation and mitochondrial dysfunction amelioration were accompanied by lower apoptosis levels in tubular cells under hyperglycemic conditions.…”

The physiological roles of autophagy in the mammalian life cycle

“…Recent studies have revealed that many ATG proteins like LC3, ATG5, PINK1, and p62 are highly expressed in human spermatozoa, especially in the middle piece of the tail where mitochondria are located (Aparicio et al ., ). Autophagy is thought to be crucial for sperm survival and motility.…”

Autophagy related gene expression status in patients diagnosed with azoospermia: A cross‐sectional study

“…autophagy was reported to be capable of protecting the function and integrity of sertoli cells by inhibiting the ectoplasmic specialization degradation. Additionally, autophagy was shown to be related to proteins that play a critically role in human sperm, and so the mitophagy (a form of autophagy) may affect different aspects of sperm function . A single examination is sufficient to determine that autophagy is an active process in sperm, and its activation may critically affect the regulation of sperm physiology and also the maintenance of viability and motility .…”