SCARB1
Encyclopedia
Scavenger receptor class B member 1 (SRB1) also known as SR-BI is a protein
that in humans is encoded by the SCARB1 gene
. SR-BI functions as a receptor for high-density lipoprotein.
Scavenger receptor
class B, type I (SR-BI) is an integral membrane protein
found in numerous cell types/tissues, including the liver
and adrenal. It is best known for its role in facilitating the uptake of cholesteryl esters from high-density lipoproteins in the liver. This process drives the movement of cholesterol
from peripheral tissues towards the liver
for excretion. This movement of cholesterol
is known as reverse cholesterol transport
and is a protective mechanism against the development of atherosclerosis
, which is the principal cause of heart disease
and stroke
.
SR-BI has also been identified in the livers of non-mammalian species (turtle
, goldfish
, shark
, chicken
, frog
, and skate
), suggesting it emerged early in vertebrate evolutionary history. The turtle also seems to upregulate SB-RI during egg development, indicating that cholesterol efflux may be at peak levels during this time of year in turtles.
In melanocytic cells SCARB1 gene expression may be regulated by the MITF
.
SCARB1 is, along with CD81
, the receptor for the entry of the Hepatitis C virus
in liver cells.
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 SCARB1 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...
. SR-BI functions as a receptor for high-density lipoprotein.
Scavenger receptor
Scavenger receptor
Scavenger receptors are a group of receptors that recognize modified low-density lipoprotein by oxidation or acetylation. This naming is based on a function of cleaning : Scavenger receptors widely recognize and uptake macromolecules having a negative charge as well as modified LDL.-Function:It is...
class B, type I (SR-BI) is an integral membrane protein
Integral membrane protein
An integral membrane protein is a protein molecule that is permanently attached to the biological membrane. Proteins that cross the membrane are surrounded by "annular" lipids, which are defined as lipids that are in direct contact with a membrane protein...
found in numerous cell types/tissues, including the liver
Liver
The liver is a vital organ present in vertebrates and some other animals. It has a wide range of functions, including detoxification, protein synthesis, and production of biochemicals necessary for digestion...
and adrenal. It is best known for its role in facilitating the uptake of cholesteryl esters from high-density lipoproteins in the liver. This process drives the movement of cholesterol
Cholesterol
Cholesterol is a complex isoprenoid. Specifically, it is a waxy steroid of fat that is produced in the liver or intestines. It is used to produce hormones and cell membranes and is transported in the blood plasma of all mammals. It is an essential structural component of mammalian cell membranes...
from peripheral tissues towards the liver
Liver
The liver is a vital organ present in vertebrates and some other animals. It has a wide range of functions, including detoxification, protein synthesis, and production of biochemicals necessary for digestion...
for excretion. This movement of cholesterol
Cholesterol
Cholesterol is a complex isoprenoid. Specifically, it is a waxy steroid of fat that is produced in the liver or intestines. It is used to produce hormones and cell membranes and is transported in the blood plasma of all mammals. It is an essential structural component of mammalian cell membranes...
is known as reverse cholesterol transport
Reverse cholesterol transport
Reverse cholesterol transport is a multi-step process resulting in the net movement of cholesterol from peripheral tissues back to the liver via the plasma....
and is a protective mechanism against the development of atherosclerosis
Atherosclerosis
Atherosclerosis is a condition in which an artery wall thickens as a result of the accumulation of fatty materials such as cholesterol...
, which is the principal cause of heart disease
Heart disease
Heart disease, cardiac disease or cardiopathy is an umbrella term for a variety of diseases affecting the heart. , it is the leading cause of death in the United States, England, Canada and Wales, accounting for 25.4% of the total deaths in the United States.-Types:-Coronary heart disease:Coronary...
and stroke
Stroke
A stroke, previously known medically as a cerebrovascular accident , is the rapidly developing loss of brain function due to disturbance in the blood supply to the brain. This can be due to ischemia caused by blockage , or a hemorrhage...
.
SR-BI has also been identified in the livers of non-mammalian species (turtle
Turtle
Turtles are reptiles of the order Testudines , characterised by a special bony or cartilaginous shell developed from their ribs that acts as a shield...
, goldfish
Goldfish
The goldfish is a freshwater fish in the family Cyprinidae of order Cypriniformes. It was one of the earliest fish to be domesticated, and is one of the most commonly kept aquarium fish....
, shark
Shark
Sharks are a type of fish with a full cartilaginous skeleton and a highly streamlined body. The earliest known sharks date from more than 420 million years ago....
, chicken
Chicken
The chicken is a domesticated fowl, a subspecies of the Red Junglefowl. As one of the most common and widespread domestic animals, and with a population of more than 24 billion in 2003, there are more chickens in the world than any other species of bird...
, frog
Frog
Frogs are amphibians in the order Anura , formerly referred to as Salientia . Most frogs are characterized by a short body, webbed digits , protruding eyes and the absence of a tail...
, and skate
Skate
Skates are cartilaginous fish belonging to the family Rajidae in the superorder Batoidea of rays. There are more than 200 described species in 27 genera. There are two subfamilies, Rajinae and Arhynchobatinae ....
), suggesting it emerged early in vertebrate evolutionary history. The turtle also seems to upregulate SB-RI during egg development, indicating that cholesterol efflux may be at peak levels during this time of year in turtles.
In melanocytic cells SCARB1 gene expression may be regulated by the MITF
Microphthalmia-associated transcription factor
Microphthalmia-associated transcription factor is a basic helix-loop-helix leucine zipper transcription factor involved in melanocyte and osteoclast development.-Clinical significance:...
.
SCARB1 is, along with CD81
CD81
CD81 molecule, also known as CD81 , is a protein which in humans is encoded by the CD81 gene...
, the receptor for the entry of the Hepatitis C virus
Hepatitis C virus
Hepatitis C virus is a small , enveloped, positive-sense single-stranded RNA virus of the family Flaviviridae...
in liver cells.