Zinc alpha 2-glycoprotein (ZAG) is a protein of interest because of its ability to play many important functions in the human body, including fertilization and lipid mobilization After the discovery of this molecule, during the last 5 decades, various studies have been documented on its structure and functions, but still, it is considered as a protein with an unknown function Its expression is regulated by glucocorticoids Due to its high sequence homology with lipid-mobilizing factor and high expression in cancer cachexia, it is considered as a novel adipokine On the other hand, structural organization and fold is similar to MHC class I antigen-presenting molecule; hence, ZAG may have a role in the expression of the immune response The function of ZAG under physiologic and cancerous conditions remains mysterious but is considered as a tumor biomarker for various carcinomas There are several unrelated functions that are attributed to ZAG, such as RNase activity, regulation of melanin production, hindering tumor proliferation, and transport of nephritic by-products This article deals with the discussion of the major aspects of ZAG from its gene structure to function and metabolism

https://mcr.aacrjournals.org/content/molcanres/6/6/892.full.pdf

Zinc alpha 2-glycoprotein: a multidisciplinary protein.

In vitro evaluation of sperm quality.

Our ability to screen the structural and functional integrity of the spermatozoon in vitro has increased markedly over the past decades, but our capacity to estimate the fertility of a semen sample or of the sire from which it has been collected, especially in selected farm animal breeders, has not. The estimation of fertility is constrained by several factors (e.g. type of cell, analysis strength, sperm deposition strategies, recordings of fertility), including the fact that the ejaculate is composed of a diverse sperm population. Such cell heterogeneity is reflected not only in differences in the intactness of attributes needed for fertilisation, such as motility or morphology, but also in the relative ability of the spermatozoa to remain fertile over time, to sustain selection steps and responses to exogenous stimuli similar to those during sperm transport in the female genital tract, all of which account for innate variations in the fertilising ability among doses, ejaculates and sires. Determination of how large such a sperm population with competence for fertilisation and in-built ability to display these attributes under physiological signalling is would allow for a better estimation o f fertility, provided that th e particular s ire produces this sub-population in a repeatable manner. The value of these analyses is discussed in the present paper.

State of the art in farm animal sperm evaluation.

Sperm are stored in the isthmic region of the oviduct under conditions that maintain viability and suppress early capacitation steps until ovulation occurs. The initial contact between sperm and oviductal epithelium is mediated by carbohydrate-protein interactions. In the pig, the carbohydrate recognition system has been shown to involve oligomannosyl structures. The spermadhesins AWN and AQN1 are the dominant porcine carbohydrate-binding sperm proteins. The objective of this study was to demonstrate that AQN1 contributes to sperm binding to the oviductal epithelium. AQN1 showed a broad carbohydrate-binding pattern as it recognizes both alpha- and beta-linked galactose as well as Manalpha1-3(Manalpha1-6)Man structures, whereas AWN bound only the galactose species. Binding of ejaculated sperm to oviductal epithelium was inhibited by addition of AQN1 but not by AWN. Mannose-binding sites were localized over the rostral region of the sperm head. Flow cytometry showed that, under capacitating conditions, the population of live sperm was shifted within 30 min toward an increase in the proportion of cells with low mannose- and high galactose-binding. The loss of mannose-binding sites was accompanied by the loss of AQN1 in sperm extracts and the significant reduction in the sperm-oviduct binding. The oviductal epithelium was shown by GNA-lectin histochemistry and by SDS-PAGE and lectin blotting of the apical membrane fraction to express mannose components that could be recognized by AQN1. These results demonstrate that the sperm lectin AQN1 fulfils the criteria for an oviduct receptor in the pig and may play a role in the formation of the oviductal sperm reservoir.

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Gabriele Volker

Papers

Detection of cooling-induced membrane changes in the response of boar sperm to capacitating conditions.

Functional significance of responsiveness to capacitating conditions in boar spermatozoa.