Abhydrolase domain-containing protein 2 is a

serine hydrolase Serine hydrolases are one of the largest known enzyme classes comprising approximately ~200 enzymes or 1% of the genes in the human proteome. A defining characteristic of these enzymes is the presence of a particular serine at the active site, whic ...

enzyme that is strongly expressed in human

spermatozoa A spermatozoon (; also spelled spermatozoön; : spermatozoa; ) is a motile sperm cell (biology), cell produced by male animals relying on internal fertilization. A spermatozoon is a moving form of the ploidy, haploid cell (biology), cell that is ...

. It is a key controller of sperm hyperactivation, which is a necessary step in allowing sperm to fertilize an

egg An egg is an organic vessel grown by an animal to carry a possibly fertilized egg cell (a zygote) and to incubate from it an embryo within the egg until the embryo has become an animal fetus that can survive on its own, at which point the ...

. It is encoded by the ''ABHD2''

gene In biology, the word gene has two meanings. The Mendelian gene is a basic unit of heredity. The molecular gene is a sequence of nucleotides in DNA that is transcribed to produce a functional RNA. There are two types of molecular genes: protei ...

Function

In the presence of

Progesterone Progesterone (; P4) is an endogenous steroid and progestogen sex hormone involved in the menstrual cycle, pregnancy, and embryogenesis of humans and other species. It belongs to a group of steroid hormones called the progestogens and is the ma ...

(or Pregnenolone Sulfate,) it cleaves 2-arachidonoylglycerol (2AG) into

glycerol Glycerol () is a simple triol compound. It is a colorless, odorless, sweet-tasting, viscous liquid. The glycerol backbone is found in lipids known as glycerides. It is also widely used as a sweetener in the food industry and as a humectant in pha ...

and

arachidonic acid Arachidonic acid (AA, sometimes ARA) is a polyunsaturated omega−6 fatty acid 20:4(ω−6), or 20:4(5,8,11,14). It is a precursor in the formation of leukotrienes, prostaglandins, and thromboxanes. Together with omega−3 fatty acids an ...

(AA). 2AG inhibits sperm calcium channel CatSper, and so when ABHD2 removes 2AG calcium flows into the cell through the CatSper channel, leading to hyperactivation. ABHD2 is inhibited by

testosterone Testosterone is the primary male sex hormone and androgen in Male, males. In humans, testosterone plays a key role in the development of Male reproductive system, male reproductive tissues such as testicles and prostate, as well as promoting se ...

, (as well as

hydrocortisone Hydrocortisone is the name for the hormone cortisol when supplied as a medication. It is a corticosteroid and works as an anti-inflammatory and by immune suppression. Uses include conditions such as adrenocortical insufficiency, adrenogenit ...

, and the plant triterpenoids lupeol and pristimerin) which may prevent premature hyperactivation.

Structure

This gene encodes a protein containing an alpha/beta hydrolase fold, which is a catalytic domain found in a very wide range of

enzyme An enzyme () is a protein that acts as a biological catalyst by accelerating chemical reactions. The molecules upon which enzymes may act are called substrate (chemistry), substrates, and the enzyme converts the substrates into different mol ...

s. Alternative splicing of this gene results in two transcript variants encoding the same protein.

Role in disease

The ''ABHD2'' gene is down regulated in the lungs of people with

Emphysema Emphysema is any air-filled enlargement in the body's tissues. Most commonly emphysema refers to the permanent enlargement of air spaces (alveoli) in the lungs, and is also known as pulmonary emphysema. Emphysema is a lower respiratory tract di ...

. Analysis of ''ABHD2'' deficiency in mice found a decrease in

phosphatidylcholine Phosphatidylcholines (PC) are a class of phospholipids that incorporate choline as a headgroup. They are a major component of biological membranes and can easily be obtained from a variety of readily available sources, such as egg yolk or soyb ...

levels. The mice developed emphysema which was attributed to an increase in

macrophage Macrophages (; abbreviated MPhi, φ, MΦ or MP) are a type of white blood cell of the innate immune system that engulf and digest pathogens, such as cancer cells, microbes, cellular debris and foreign substances, which do not have proteins that ...

infiltration, increased inflammatory

cytokine Cytokines () are a broad and loose category of small proteins (~5–25 kDa) important in cell signaling. Cytokines are produced by a broad range of cells, including immune cells like macrophages, B cell, B lymphocytes, T cell, T lymphocytes ...

levels, an imbalance of protease/anti-protease, and an increase in

cell death Cell death is the event of a biological cell ceasing to carry out its functions. This may be the result of the natural process of old cells dying and being replaced by new ones, as in programmed cell death, or may result from factors such as di ...

. This research suggests that ABHD2 is important in maintaining the structural integrity of the lungs, and that disruption of phospholipid metabolism in the alveoli may lead to the development of emphysema. Increased expression has also been seen in the lungs of smokers. ''ABHD2'' is also expressed in

atherosclerotic Atherosclerosis is a pattern of the disease arteriosclerosis, characterized by development of abnormalities called lesions in walls of arteries. This is a chronic inflammatory disease involving many different cell types and is driven by elev ...

lesions. Expression has been found to be higher in patients with unstable angina than in patients with stable angina. Up-regulation of ''ABHD2'' has been observed in cells transfected with

Hepatitis B virus Hepatitis B virus (HBV) is a partially double-stranded DNA virus, a species of the genus '' Orthohepadnavirus'' and a member of the '' Hepadnaviridae'' family of viruses. This virus causes the disease hepatitis B. Classification Hepatitis B ...

(HBV) DNA (HepG2.2.15 cells). Expression was down-regulated by the drug

lamivudine Lamivudine, commonly called 3TC, is an antiretroviral medication used to prevent and treat HIV/AIDS. It is also used to treat chronic hepatitis B when other options are not possible. It is effective against both HIV-1 and HIV-2. It is typi ...

, used in the treatment of hepatitis B. It has been suggested that ABHD2 has an important role in HBV propagation and could be a potential drug target in the treatment of hepatitis B. Suppression of ABHD2 has been linked to poor prognoses in ovarian cancer and resistance to platinum-based chemotherapy drugs.

Function

Structure

Role in disease

References

External links

Further reading