Podosome
Encyclopedia
Podosomes are small cylindrical ECM adhesion structures approximately 0.5 um in diameter. They contain focal contact proteins like vinculin
and paxillin
and are found primarily in malignant cells. They can also be found in normal cells such as macrophages and osteoclasts. All podosomes contain gelsolin
and dynamin
proteins.
They are the primary sites of integrin
stimulated actin
polymerization in leukocytes of the monocytic lineage. B cells have also been reported to form podosomes. Podosomes are similar in composition and structure to the invadopodia
found in fibroblasts transformed with the v-Src oncogene
which are matrix-degrading and whose formation is associated with increased tumor
cell
invasiveness.
In myeloid
cells, podosomes are necessary for directional movement and trans-cellular diapedesis at sites of inflammation. In osteoclasts, podosomes are thought to aid in the creation of sealing rings associated with the area of bone resorption
.
Unlike focal contacts in fibroblasts and epithelial cells, the formation of podosomes does not require protein synthesis.
Vinculin
In mammalian cells, vinculin is a membrane-cytoskeletal protein in focal adhesion plaques that is involved in linkage of integrin adhesion molecules to the actin cytoskeleton...
and paxillin
Paxillin
Paxillin is a signal transduction adaptor protein discovered in 1990 in the laboratory of Keith Burridge and should not be confused with the neurotoxin paxilline. The C-terminal region of paxillin contains four LIM domains that target paxillin to focal adhesions, it is presumed through a direct...
and are found primarily in malignant cells. They can also be found in normal cells such as macrophages and osteoclasts. All podosomes contain gelsolin
Gelsolin
Gelsolin is an actin-binding protein that is a key regulator of actin filament assembly and disassembly. Gelsolin is one of the most potent members of the actin-severing gelsolin/villin superfamily, as it severs with nearly 100% efficiency...
and dynamin
Dynamin
Dynamin is a GTPase responsible for endocytosis in the eukaryotic cell. Dynamins are principally involved in the scission of newly formed vesicles from the membrane of one cellular compartment and their targeting to, and fusion with, another compartment, both at the cell surface as well as at the...
proteins.
They are the primary sites of integrin
Integrin
Integrins are receptors that mediate attachment between a cell and the tissues surrounding it, which may be other cells or the ECM. They also play a role in cell signaling and thereby regulate cellular shape, motility, and the cell cycle....
stimulated actin
Actin
Actin is a globular, roughly 42-kDa moonlighting protein found in all eukaryotic cells where it may be present at concentrations of over 100 μM. It is also one of the most highly-conserved proteins, differing by no more than 20% in species as diverse as algae and humans...
polymerization in leukocytes of the monocytic lineage. B cells have also been reported to form podosomes. Podosomes are similar in composition and structure to the invadopodia
Invadopodia
Invadopodia or invasive feet are protrusions in the cell membrane of some cells that are rich in actin and extend into the extracellular matrix . Researchers have reported that invadopodia formation is initiated with the assembly of actin core structures, followed by the accumulation of mtrix...
found in fibroblasts transformed with the v-Src oncogene
Oncogene
An oncogene is a gene that has the potential to cause cancer. In tumor cells, they are often mutated or expressed at high levels.An oncogene is a gene found in the chromosomes of tumor cells whose activation is associated with the initial and continuing conversion of normal cells into cancer...
which are matrix-degrading and whose formation is associated with increased tumor
Tumor
A tumor or tumour is commonly used as a synonym for a neoplasm that appears enlarged in size. Tumor is not synonymous with cancer...
cell
Cell (biology)
The cell is the basic structural and functional unit of all known living organisms. It is the smallest unit of life that is classified as a living thing, and is often called the building block of life. The Alberts text discusses how the "cellular building blocks" move to shape developing embryos....
invasiveness.
In myeloid
Myeloid
The term myeloid suggests an origin in the bone marrow or spinal cord, or a resemblance to the marrow or spinal cord.In hematopoiesis, the term "myeloid cell" is used to describe any leukocyte that is not a lymphocyte...
cells, podosomes are necessary for directional movement and trans-cellular diapedesis at sites of inflammation. In osteoclasts, podosomes are thought to aid in the creation of sealing rings associated with the area of bone resorption
Bone resorption
Bone resorption is the process by which osteoclasts break down bone and release the minerals, resulting in a transfer of calcium from bone fluid to the blood....
.
Unlike focal contacts in fibroblasts and epithelial cells, the formation of podosomes does not require protein synthesis.
External links
- Podosomes and Invadopodia at Scirus Topic Pages