Filamins are a class of proteins that hold two

actin filament Microfilaments, also called actin filaments, are protein filaments in the cytoplasm of eukaryotic cells that form part of the cytoskeleton. They are primarily composed of polymers of actin, but are modified by and interact with numerous other p ...

s at large angles. Filamin protein in mammals is made up of an actin-binding domain at its

N-terminus The N-terminus (also known as the amino-terminus, NH2-terminus, N-terminal end or amine-terminus) is the start of a protein or polypeptide, referring to the free amine group (-NH2) located at the end of a polypeptide. Within a peptide, the amin ...

that is followed by 24 immunoglobulin-like repeat modules of roughly 95

amino acids Amino acids are organic compounds that contain both amino and carboxylic acid functional groups. Although over 500 amino acids exist in nature, by far the most important are the Proteinogenic amino acid, 22 α-amino acids incorporated into p ...

. There are two hinge regions; between repeats 15-16 and 23-24. Filamin gets cleaved at these hinge regions to generate smaller fragments of the protein. Filamin has two actin-binding sites with a V-linkage between them, so that it cross-links actin filaments into a network with the filaments orientated almost at right angles to one another. Filamin proteins include: * FLNA * FLNB * FLNC Over-expression of FLNA stops the regeneration of bladder carcinoma (BC) cells, by inhibiting the

cell cycle The cell cycle, or cell-division cycle, is the sequential series of events that take place in a cell (biology), cell that causes it to divide into two daughter cells. These events include the growth of the cell, duplication of its DNA (DNA re ...

and inducing

apoptosis Apoptosis (from ) is a form of programmed cell death that occurs in multicellular organisms and in some eukaryotic, single-celled microorganisms such as yeast. Biochemistry, Biochemical events lead to characteristic cell changes (Morphology (biol ...

of BC cells. FLNA has also been shown to reduce the

mobility Mobility may refer to: Social sciences and humanities * Economic mobility, ability of individuals or families to improve their economic status * Geographic mobility, the measure of how populations and goods move over time * Mobilities, a conte ...

and invasion abilities of BC cells.

FLNA

The FLNa protein is also known for having an important structural function in the cardiovascular system. In particular, it has been studied by the American Society of Hematology for its role in platelet function in the blood.

Platelets Platelets or thrombocytes () are a part of blood whose function (along with the coagulation factors) is to react to bleeding from blood vessel injury by clumping to form a blood clot. Platelets have no cell nucleus; they are fragments of cyto ...

are known for their role in wound repair as they are able to aggregate and stop bleeding.

Megakaryocytes A megakaryocyte () is a large bone marrow cell with a lobated nucleus that produces blood platelets (thrombocytes), which are necessary for normal clotting. In humans, megakaryocytes usually account for 1 out of 10,000 bone marrow cells, but ca ...

allow for the production of platelets. However, mutations in the FLNa gene have been found to disrupt the process of healing as they limit the production of giant platelets that are needed for healing. This condition is known as Macrothrombocytopenia.

FLNC

The FLNC protein is important to the functioning of cardiac and skeletal tissue. In particular, mutations to the FLNC can have detrimental effects on cardiac tissue. The FLNC proteins have an important role in the structure of cardiac muscle. They contribute to the z-disk proteins which are heavily found in both cardiac and skeletal muscle tissue. Many studies have been conducted to evaluate the effects of mutations on the FLNC gene to patients that are otherwise healthy in terms of their heart. Studies conducted by the American College of Cardiology Foundation show that missense mutations in the FLNC gene could be precursors for diverse cardiomyopathies. Specifically,

hypertrophic cardiomyopathy Hypertrophic cardiomyopathy (HCM, or HOCM when obstructive) is a condition in which muscle tissues of the heart become thickened without an obvious cause. The parts of the heart most commonly affected are the interventricular septum and the ...

(HCM) and restrictive cardiomyopathy (RCM) were noted. A further investigation of the link between this protein and cardiac tissue could allow professionals to develop treatments to prevent and treat patients with FLNC mutation induced cardiomyopathies.

References

External links

* {{Cytoskeletal proteins Human proteins Proteins