Biology Reference
In-Depth Information
b
-arrestins have identified important roles of these adaptor molecules in
immune responses, and regulation of the pathogenesis of several disease pro-
cesses has begun to be explored.
The immune system consists of innate and adaptive responses. Innate
immune cells, receptor systems, and related signaling pathways defend the
host from infections such as bacteria and viruses, as well as from non-
infectious tissue injuries. Defense by the innate immune system includes
chemotaxis of inflammatory cells, release of cytokines, pathogen clearance,
as well as the activation of the adaptive immune system through antigen
presentation. The adaptive immune system, on the other hand, consists of
highly specialized cells (such as T lymphocytes and B lymphocytes), pro-
teins, and processes that aim to further eliminate pathogens. In addition
to their role in pathogen clearance, both systems have a role in tissue injury,
inflammation, and repair processes. Expression of
b
-arrestins has been
found in innate immune cells, such as macrophages and polymorphonuclear
leukocytes (PMNs), as well as in adaptive immune cells, including T lym-
phocytes and B cells.
b
-Arrestins have been suggested to have a role in both
systems. In addition,
b
-arrestins may have a role in mammalian hematopoi-
esis as
b
-arrestin 1-deficient mice demonstrate basal hematologic defects.
20
Similarly in zebrafish,
b
-arrestin 1 relieves polycomb group-mediated
repression of the cdx4-hox pathway, regulating hematopoietic lineage spec-
ification during primitive hematopoiesis.
20
2.
b
-ARRESTINS IN INNATE IMMUNITY
2.1.
-Arrestins and macrophages
b
-Arrestins are expressed in macrophages. Both
b
-arrestins 1 and 2 mRNA
and protein expression are found in human and mouse mononuclear cells
and macrophages.
21,22
Lipopolysaccharides downregulate
b
-arrestin 2 expres-
sion in RAW264 macrophages.
23
Furthermore,
b
-arrestin 1 expression
can be downregulated by the activation of TLR2 and TLR4 in primary
mouse macrophages, and the regulation is both transcriptional and posttransla-
tional.
24
Expression of
b
-arrestins 1 and 2 by macrophages can be regulated by
cytokines. The cytokine, granulocyte-macrophage colony-stimulating factor-
1, increased
b
-arrestin 1 expression associated with the downregulation of
surface chemokine receptor CXCR4 expression in human primary mono-
cytes-macrophages.
25
Lectin phytoemagglutinin reduces
b
-arrestin 1 expres-
sion in mononuclear leukocytes, and interferon
b
-1a can quench the effect of
phytoemagglutinin on the expression of
b
-arrestin 1.
26
b
b
-Arrestin2mRNA
Search WWH ::
Custom Search