Lipocalin-1 is a

protein Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residue (biochemistry), residues. Proteins perform a vast array of functions within organisms, including Enzyme catalysis, catalysing metab ...

that in humans is encoded by the ''LCN1''

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 ...

. The protein encoded by this gene belongs to the

lipocalin The lipocalins are a family of proteins which transport small hydrophobic molecules such as steroids, bilins, retinoids, and lipids, and most lipocalins are also able to bind to complexed iron (via siderophores or flavonoids) as well as heme. Th ...

family. Lipocalins are a group of extracellular proteins that are able to bind lipophiles by enclosure within their structures to minimize solvent contact. This protein may bind hydrophobic ligands and inhibit cysteine proteinases. It may also play a role in taste reception.

Structure

Proteins are classified into the lipocalin family by their 8 antiparallel beta-sheets that form a barrel structure which acts as the binding site for ligands.

Function

Lipocalin-1 (LCN1) is capable of binding a wide variety of lipophilic molecules along with zinc and chloride ions. Because of this feature, LCN1’s main function is thought to be the removal of potentially harmful lipids and lipophilic molecules from the body by binding them. The LCN1-Ligand complex is then imported via Lipocalin-1-Interacting Membrane Receptor (LIMR) so the bound molecule can be broken down safely within the cell. This process of retrieving molecules may impact several processes including pheromone signaling, immunodulation,

inflammation Inflammation (from ) is part of the biological response of body tissues to harmful stimuli, such as pathogens, damaged cells, or irritants. The five cardinal signs are heat, pain, redness, swelling, and loss of function (Latin ''calor'', '' ...

, detoxification, tissue development,

apoptosis Apoptosis (from ) is a form of programmed cell death that occurs in multicellular organisms and in some eukaryotic, single-celled microorganisms such as yeast. Biochemistry, Biochemical events lead to characteristic cell changes (Morphology (biol ...

and more. LCN1 shares three sequence motifs with cystatins which enables LCN1 to act in a similar manner to cystatins as a cysteine proteinase inhibitor. These domains have specifically been shown to bind

Papain Papain, also known as papaya proteinase I, is a cysteine protease () enzyme present in papaya (''Carica papaya'') and mountain papaya (''Vasconcellea cundinamarcensis''). It is the namesake member of the papain-like protease family. It has wi ...

. LCN1 also plays a role in stabilizing the lipid layer of the

tear film Tear, tears or tearing may refer to: * Tearing, the act of breaking apart a material by force * Tears, a clear liquid secreted by the tear gland in the eyes of land mammals Arts and entertainment Literature * "Tears", a poem by Edward Thomas ...

, though the details of this are not yet well understood.

History

Lipocalin-1 was initially thought to be produced exclusively by

exocrine glands Exocrine glands are glands that secrete substances onto an epithelial surface by way of a duct. Examples of exocrine glands include sweat, salivary, mammary, ceruminous, lacrimal, sebaceous, prostate and mucous. Exocrine glands are one of ...

but has also been found in corticotrophs of the

pituitary gland The pituitary gland or hypophysis is an endocrine gland in vertebrates. In humans, the pituitary gland is located at the base of the human brain, brain, protruding off the bottom of the hypothalamus. The pituitary gland and the hypothalamus contr ...

. Alternate Names: Human Tear Prealbumin, Tear Lipocalin, von Ebner’s Gland Protein

Clinical

When a cell is under stress, due to inflammation, infection, or otherwise, it will produce elevated levels of lipocalin-1 (LCN1). This makes it a potential noninvasive biomarker for various diseases. This potential has been shown in a study of

IVF In vitro fertilisation (IVF) is a process of fertilisation in which an egg is combined with sperm in vitro ("in glass"). The process involves monitoring and stimulating the ovulatory process, then removing an ovum or ova (egg or eggs) from t ...

blastocysts The blastocyst is a structure formed in the early embryonic development of mammals. It possesses an inner cell mass (ICM) also known as the ''embryoblast'' which subsequently forms the embryo, and an outer layer of trophoblast cells called the ...

, where elevated levels of LCN1 indicated

aneuploidy Aneuploidy is the presence of an abnormal number of chromosomes in a cell (biology), cell, for example a human somatic (biology), somatic cell having 45 or 47 chromosomes instead of the usual 46. It does not include a difference of one or more plo ...

in the blastocyst.

Structure

Function

History

Clinical

References

Further reading