Recent from talks
Haptoglobin
Knowledge base stats:
Talk channels stats:
Members stats:
Haptoglobin
Haptoglobin (abbreviated as Hp) is the protein that in humans is encoded by the HP gene. In blood plasma, haptoglobin binds with high affinity to free hemoglobin released from erythrocytes, and thereby inhibits its deleterious oxidative activity. Compared to Hp, hemopexin binds to free heme. The haptoglobin-hemoglobin complex will then be removed by the reticuloendothelial system (mostly the spleen).
In clinical settings, the haptoglobin assay is used to screen for and monitor intravascular hemolytic anemia. In intravascular hemolysis, free hemoglobin will be released into circulation and hence haptoglobin will bind the hemoglobin. This causes a decline in haptoglobin levels.
The protein was discovered as a "plasma substance" in 1938 by French biochemists Max-Fernand Jayle and Michel Polonovski.
Hemoglobin that has been released into the blood plasma by damaged red blood cells has harmful effects. The HP gene encodes a preproprotein that is processed to yield both alpha and beta chains, which subsequently combines as a tetramer to produce haptoglobin. Haptoglobin functions to bind the free plasma hemoglobin, which allows degradative enzymes to gain access to the hemoglobin while at the same time preventing loss of iron through the kidneys and protecting the kidneys from damage by hemoglobin.
The cellular receptor target of Hp is the monocyte/macrophage scavenger receptor, CD163. Following Hb-Hp binding to CD163, cellular internalization of the complex leads to globin and heme metabolism, which is followed by adaptive changes in antioxidant and iron metabolism pathways and macrophage phenotype polarization.
Hp has hemoglobin-independent immunomodulatory functions. It dampens lipopolysaccharide-induced cytokine expression. Lipopolysaccharides directly bind to Hp, which, due to the high abundance of Hp in serum, results in their buffering and shielding from toll-like receptor 4. Functionally, this results in delayed activation of the NF-κB pathway.
When hemoglobin is released from RBCs within the physiologic range of haptoglobin, the potential deleterious effects of hemoglobin are prevented. During hyper-hemolytic conditions or with chronic hemolysis, haptoglobin is depleted and hemoglobin readily distributes to tissues where it might be exposed to oxidative conditions. In such conditions, heme can be released from ferric (Fe3+-bound) hemoglobin. The free heme can then accelerate tissue damage by promoting peroxidative reactions and activation of inflammatory cascades. Hemopexin (Hx) is another plasma glycoprotein that is able to bind heme with high affinity. It sequesters heme in an inert non-toxic form and transports it to the liver for catabolism and excretion.
Haptoglobin is produced mostly by hepatic cells but also by other tissues such as skin, lung and kidney. In addition, the haptoglobin gene is expressed in murine and human adipose tissue.
Hub AI
Haptoglobin AI simulator
(@Haptoglobin_simulator)
Haptoglobin
Haptoglobin (abbreviated as Hp) is the protein that in humans is encoded by the HP gene. In blood plasma, haptoglobin binds with high affinity to free hemoglobin released from erythrocytes, and thereby inhibits its deleterious oxidative activity. Compared to Hp, hemopexin binds to free heme. The haptoglobin-hemoglobin complex will then be removed by the reticuloendothelial system (mostly the spleen).
In clinical settings, the haptoglobin assay is used to screen for and monitor intravascular hemolytic anemia. In intravascular hemolysis, free hemoglobin will be released into circulation and hence haptoglobin will bind the hemoglobin. This causes a decline in haptoglobin levels.
The protein was discovered as a "plasma substance" in 1938 by French biochemists Max-Fernand Jayle and Michel Polonovski.
Hemoglobin that has been released into the blood plasma by damaged red blood cells has harmful effects. The HP gene encodes a preproprotein that is processed to yield both alpha and beta chains, which subsequently combines as a tetramer to produce haptoglobin. Haptoglobin functions to bind the free plasma hemoglobin, which allows degradative enzymes to gain access to the hemoglobin while at the same time preventing loss of iron through the kidneys and protecting the kidneys from damage by hemoglobin.
The cellular receptor target of Hp is the monocyte/macrophage scavenger receptor, CD163. Following Hb-Hp binding to CD163, cellular internalization of the complex leads to globin and heme metabolism, which is followed by adaptive changes in antioxidant and iron metabolism pathways and macrophage phenotype polarization.
Hp has hemoglobin-independent immunomodulatory functions. It dampens lipopolysaccharide-induced cytokine expression. Lipopolysaccharides directly bind to Hp, which, due to the high abundance of Hp in serum, results in their buffering and shielding from toll-like receptor 4. Functionally, this results in delayed activation of the NF-κB pathway.
When hemoglobin is released from RBCs within the physiologic range of haptoglobin, the potential deleterious effects of hemoglobin are prevented. During hyper-hemolytic conditions or with chronic hemolysis, haptoglobin is depleted and hemoglobin readily distributes to tissues where it might be exposed to oxidative conditions. In such conditions, heme can be released from ferric (Fe3+-bound) hemoglobin. The free heme can then accelerate tissue damage by promoting peroxidative reactions and activation of inflammatory cascades. Hemopexin (Hx) is another plasma glycoprotein that is able to bind heme with high affinity. It sequesters heme in an inert non-toxic form and transports it to the liver for catabolism and excretion.
Haptoglobin is produced mostly by hepatic cells but also by other tissues such as skin, lung and kidney. In addition, the haptoglobin gene is expressed in murine and human adipose tissue.
Recent media