Prolactin-inducible protein also known as gross cystic disease fluid protein 15 (GCDFP-15) or BRST2 is a protein

Protein

Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...

 that in humans is encoded by the PIP gene

Gene

A gene is a molecular unit of heredity of a living organism. It is a name given to some stretches of DNA and RNA that code for a type of protein or for an RNA chain that has a function in the organism. Living beings depend on genes, as they specify all proteins and functional RNA chains...

. It is upregulated by prolactin

Prolactin

Prolactin also known as luteotropic hormone is a protein that in humans is encoded by the PRL gene.Prolactin is a peptide hormone discovered by Henry Friesen...

 and androgens and downregulated by estrogen

Estrogen

Estrogens , oestrogens , or œstrogens, are a group of compounds named for their importance in the estrous cycle of humans and other animals. They are the primary female sex hormones. Natural estrogens are steroid hormones, while some synthetic ones are non-steroidal...

.

Function

The protein has a physiological function in regulation of water transport mainly in apocrine glands in the axilla, vulva, eyelid, and ear canal serous cells of the submandibular salivary gland, serous cells of the submucosal glands of the bronchi, and accessory lacrimal glands as well as cutaneous eccrine glands.

PIP has the ability to bind immunoglobulin G (IgG), IgG-Fc, CD4-T cell receptor suggesting a wide range of immunological functions. PIP also binds to AZGP1

AZGP1

Zinc-alpha-2-glycoprotein is a protein that in humans is encoded by the AZGP1 gene.This gene expresses a soluble protein that stimulates lipolysis, induces a reduction in body fat in mice, is associated with the cachexia related to cancer, and is known to be expressed in secretory cells of lung...

 and fibronectin

Fibronectin

Fibronectin is a high-molecular weight glycoprotein of the extracellular matrix that binds to membrane-spanning receptor proteins called integrins. In addition to integrins, fibronectin also binds extracellular matrix components such as collagen, fibrin and heparan sulfate proteoglycans...

.

Use as marker and significance in disease

Prolactin induced protein (called GCDFP-15 in this context) in breast cyst fluid or breast tissue serves as marker of both benign and malignant apocrine metaplasia as the protein is not normally expressed in breast tissue. It is characteristic of low grade apocrine carcinoma of the breast, high grade apocrine carcinoma frequently loose expression of this marker.

A mitogenic effect of this protein on experimental breast cells lines MCF10A, MCF7, BT474, MDA-MB231 and T47D was detected. Prolactin-induced protein has also been used for identification and detection of disseminated breast cancer

Breast cancer

Breast cancer is cancer originating from breast tissue, most commonly from the inner lining of milk ducts or the lobules that supply the ducts with milk. Cancers originating from ducts are known as ductal carcinomas; those originating from lobules are known as lobular carcinomas...

 cells

In T47D breast cancer cells, androgen receptor and RUNX2

Runx2

Runt-related transcription factor 2 also known as core-binding factor subunit alpha-1 is a protein that in humans is encoded by the RUNX2 gene RUNX2 is a key transcription factor associated with osteoblast differentiation....

 interact to synergistically enhance PIP expression.

It has been hypothesized that in Sjögren's syndrome

Sjögren's syndrome

Sjögren's syndrome , also known as "Mikulicz disease" and "Sicca syndrome", is a systemic autoimmune disease in which immune cells attack and destroy the exocrine glands that produce tears and saliva....

 PIP binds to the C-terminal portion of aquaporin-5

AQP5

Aquaporin-5 is a protein that in humans is encoded by the AQP5 gene.- External links :...

and causes it to be transported to the apical membrane causing disruptions of water transport.

External links

• BRST2 immunostaining - abcam.com.
• GCDFP-15 immunostaining - immunosaver.com.