Retinol binding protein 4
Encyclopedia
Retinol binding protein 4, plasma, also known as RBP4, is protein
that in humans is encoded by the RBP4 gene
.
family and is the specific carrier for retinol
(vitamin A alcohol) in the blood. It delivers retinol from the liver stores to the peripheral tissues. In plasma, the RBP-retinol complex interacts with transthyretin
, which prevents its loss by filtration through the kidney glomeruli
. A deficiency of vitamin A blocks secretion of the binding protein posttranslationally and results in defective delivery and supply to the epidermal cells.
that contributes to insulin resistance
in the AG4KO mouse model. It is secreted by adipocyte
s, and can act as a signal to other cells, when there is a decrease in plasma glucose concentration.
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 RBP4 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...
.
Function
This protein belongs to the lipocalinLipocalin
The lipocalins are a family of proteins which transport small hydrophobic molecules such as steroids, bilins, retinoids, and lipids. They share limited regions of sequence homology and a common tertiary structure architecture...
family and is the specific carrier for retinol
Retinol
Retinol is one of the animal forms of vitamin A. It is a diterpenoid and an alcohol. It is convertible to other forms of vitamin A, and the retinyl ester derivative of the alcohol serves as the storage form of the vitamin in animals....
(vitamin A alcohol) in the blood. It delivers retinol from the liver stores to the peripheral tissues. In plasma, the RBP-retinol complex interacts with transthyretin
Transthyretin
Transthyretin is a serum and cerebrospinal fluid carrier of the thyroid hormone thyroxine and retinol binding protein bound to retinol. This is how transthyretin gained its name, transports thyroxine and retinol...
, which prevents its loss by filtration through the kidney glomeruli
Glomerulus
A glomerulus is a capillary tuft that is involved in the first step of filtering blood to form urine.A glomerulus is surrounded by Bowman's capsule, the beginning component of nephrons in the vertebrate kidney. A glomerulus receives its blood supply from an afferent arteriole of the renal...
. A deficiency of vitamin A blocks secretion of the binding protein posttranslationally and results in defective delivery and supply to the epidermal cells.
Clinical significance
Retinol-binding protein 4 has recently been described as an adipokineAdipokine
The adipokines or adipocytokines are cytokines secreted by adipose tissue.Members include:* chemerin* interleukin-6...
that contributes to insulin resistance
Insulin resistance
Insulin resistance is a physiological condition where the natural hormone insulin becomes less effective at lowering blood sugars. The resulting increase in blood glucose may raise levels outside the normal range and cause adverse health effects, depending on dietary conditions. Certain cell types...
in the AG4KO mouse model. It is secreted by adipocyte
Adipocyte
However, in some reports and textbooks, the number of fat cell increased in childhood and adolescence. The total number is constant in both obese and lean adult...
s, and can act as a signal to other cells, when there is a decrease in plasma glucose concentration.