Autocrine signalling
Encyclopedia
Autocrine signaling is a form of signalling in which a cell secretes a hormone or chemical messenger (called the autocrine agent) that binds to autocrine receptors on the same cell, leading to changes in the cell. This can be contrasted with paracrine signalling
, intracrine
signalling, or classical endocrine signalling.
interleukin-1 in monocytes. When interleukin-1 is produced in response to external stimuli, it can bind to cell-surface receptors
on the same cell that produced it.
Another example occurs in activated T cell
lymphocytes, i.e., when a T cell is induced to mature by binding to a peptide
:MHC
complex on a professional antigen-presenting cell
and by the B7
:CD28
costimulatory signal. Upon activation, "low-affinity" IL-2 receptors are replaced by "high-affinity" IL-2 receptors consisting of α, β, and γ chains. The cell then releases IL-2, which binds to its own new IL-2 receptors, causing self-stimulation and ultimately a monoclonal
population of T cells. These T cells can then go on to perform effector functions such as macrophage
activation, B cell
activation, and cell-mediated cytoxicity.
Paracrine signalling
Paracrine signalling is a form of cell signalling in which the target cell is near the signal-releasing cell.-Local action:Some signalling molecules degrade very quickly, limiting the scope of their effectiveness to the immediate surroundings...
, intracrine
Intracrine
Intracrine refers to a hormone that acts inside a cell. Steroid hormones act through intracellular receptors and, thus, may be considered to be intracrines. In contrast, peptide or protein hormones, in general, act as endocrines, autocrines, or paracrines by binding to their receptors present on...
signalling, or classical endocrine signalling.
Examples
An example of an autocrine agent is the cytokineCytokine
Cytokines are small cell-signaling protein molecules that are secreted by the glial cells of the nervous system and by numerous cells of the immune system and are a category of signaling molecules used extensively in intercellular communication...
interleukin-1 in monocytes. When interleukin-1 is produced in response to external stimuli, it can bind to cell-surface receptors
Receptor (biochemistry)
In biochemistry, a receptor is a molecule found on the surface of a cell, which receives specific chemical signals from neighbouring cells or the wider environment within an organism...
on the same cell that produced it.
Another example occurs in activated T cell
T cell
T cells or T lymphocytes belong to a group of white blood cells known as lymphocytes, and play a central role in cell-mediated immunity. They can be distinguished from other lymphocytes, such as B cells and natural killer cells , by the presence of a T cell receptor on the cell surface. They are...
lymphocytes, i.e., when a T cell is induced to mature by binding to a peptide
Peptide
Peptides are short polymers of amino acid monomers linked by peptide bonds. They are distinguished from proteins on the basis of size, typically containing less than 50 monomer units. The shortest peptides are dipeptides, consisting of two amino acids joined by a single peptide bond...
:MHC
MHC
-Biology:*Myosin heavy chain - part of the motor protein myosin's quaternary protein structure*Major histocompatibility complex - a highly polymorphic region on chromosome 6 with genes particularly involved in immune functions-Colleges:...
complex on a professional antigen-presenting cell
Antigen-presenting cell
An antigen-presenting cell or accessory cell is a cell that displays foreign antigen complexes with major histocompatibility complex on their surfaces. T-cells may recognize these complexes using their T-cell receptors...
and by the B7
B7 (protein)
B7 is a type of peripheral membrane protein found on activated antigen presenting cells that, when paired with either a CD28 or CD152 surface protein on a T cell, can produce a costimulatory signal to enhance or decrease the activity of a MHC-TCR signal between the APC and the T cell, respectively...
:CD28
CD28
CD28 is one of the molecules expressed on T cells that provide co-stimulatory signals, which are required for T cell activation. CD28 is the receptor for CD80 and CD86 . When activated by Toll-like receptor ligands, the CD80 expression is upregulated in antigen presenting cells...
costimulatory signal. Upon activation, "low-affinity" IL-2 receptors are replaced by "high-affinity" IL-2 receptors consisting of α, β, and γ chains. The cell then releases IL-2, which binds to its own new IL-2 receptors, causing self-stimulation and ultimately a monoclonal
Monoclonal
Monoclonal cells are defined as a group of cells produced from a single ancestral cell by repeated cellular replication. Thus they can be said to form a single "clone". The process of replication can occur in vivo, or may be stimulated in vitro for laboratory manipulations...
population of T cells. These T cells can then go on to perform effector functions such as macrophage
Macrophage
Macrophages are cells produced by the differentiation of monocytes in tissues. Human macrophages are about in diameter. Monocytes and macrophages are phagocytes. Macrophages function in both non-specific defense as well as help initiate specific defense mechanisms of vertebrate animals...
activation, B cell
B cell
B cells are lymphocytes that play a large role in the humoral immune response . The principal functions of B cells are to make antibodies against antigens, perform the role of antigen-presenting cells and eventually develop into memory B cells after activation by antigen interaction...
activation, and cell-mediated cytoxicity.