RBP4

Retinol-binding protein 4 (RBP4) is the specific carrier for retinol (also known as vitamin A), and is responsible for the conversion of unstable and insoluble retinol in aqueous solution into stable and soluble complex in plasma through their tight interaction. As a member of the lipocalin superfamily, RBP4 containing a β-barrel structure with a well-defined cavity is secreted from the liver, and in turn delivers retinol from the liver stores to the peripheral tissues. In plasma, the RBP4-retinol complex interacts with transthyretin (TTR), and this binding is crucial for preventing RBP4 excretion through the kidney glomeruli. RBP4 expressed from an ectopic source efficiently delivers retinol to the eyes, and its deficiency affects night vision largely. Recently, RBP4 as an adipokine, is found to be expressed in adipose tissue and correlated with obesity, insulin resistance (IR) and type 2 diabetes (T2DM).

RBP4 Related Areas

Immunology>>Innate Immunity>>Acute Phase Proteins>>RBP4

RBP4 Alternative Names

RBP4, RBP-4, PRO2222, OTTHUMP00000020115, PRBP, RBP [Homo sapiens]

Rbp4, Rbp-4, PRBP, RBP [Mus musculus]

Rbp4, RBPA, PRBP, RBP [Rattus norvegicus]

Summaries for RBP4

Entrez Gene summary for RBP4:

RBP4 belongs to the lipocalin family and is the specific carrier for retinol (vitamin A alcohol) in the blood. RBP4 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. [provided by RefSeq, Jul 2008]

OMIM - description for RBP4:

RBP4 is the specific carrier for retinol (vitamin A alcohol) in the blood.

Wikipedia summary for RBP4:

Retinol binding protein 4, plasma, also known as RBP4, is protein that in humans is encoded by the RBP4 gene.

Human RBP4 Protein General Information

 

• Protein names: Retinol-binding protein 4
• Sequence length: 201 AA.
• Sequence similarities: RBP4 belongs to the calycin superfamily. Lipocalin family.
• Sequence caution: The sequence AAF69622.1 differs from that shown. Reason: Erroneous initiation.
• Subcellular location: Secreted.
• Mass spectrometry: Molecular mass is 21063.46±1.88 Da from positions 17 - 199. Determined by ESI. Molecular mass is 20534 Da from positions 19 - 197. Determined by MALDI.
  Molecular mass is 20162 Da from positions 19 - 194. Determined by MALDI.
• Involvement in disease: Defects in RBP4 are a cause of retinol-binding protein deficiency (RBP deficiency) [MIM:180250]. This condition causes night vision problems. It produces a typical 'fundus xerophthalmicus', featuring a progressed atrophy of the retinal pigment epithelium.

General information above from UniProt

Function for RBP4 Protein

UniProtKB:

RBP4 delivers retinol from the liver stores to the peripheral tissues. In plasma, the RBP-retinol complex interacts with transthyretin, this prevents its loss by filtration through the kidney glomeruli.

Genatlas:

• RBP4 is delivery of retinol from the liver stores to peripheral tissues
• RBP4 is adipocyte-derived 'signal' that may contribute to the pathogenesis of type 2 diabetes
• RBP4 is adipokine, linking glucose uptake in adipocytes with systemic insulin sensitivity
• RBP4 is secreted by adipocytes, and associated with insulin resistance
• RBP4 is adipocytokine that may link obesity and insulin resistance
• RBP4 secretion was restricted to mature adipocytes, further indicating that RBP4 is strongly related to differentiation of adipocytes
• RBP4 has a robust acute effect of enhancement of NO production via stimulation of part of the PI3K/Akt/eNOS pathway and inhibition of ERK1/2 phosphorylation which results in vasodilatation

Phenotype Information for RBP4

• Gene/Locus: RBP4
• Phenotype: Retinol binding protein, deficiency of

Phenotype Information for RBP4 from OMIM (Online Mendelian Inheritance in Man)