Chloride intracellular channel protein 5 is a

protein Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residue (biochemistry), residues. Proteins perform a vast array of functions within organisms, including Enzyme catalysis, catalysing metab ...

that in humans is encoded by the ''CLIC5''

gene In biology, the word gene has two meanings. The Mendelian gene is a basic unit of heredity. The molecular gene is a sequence of nucleotides in DNA that is transcribed to produce a functional RNA. There are two types of molecular genes: protei ...

Expression and localization

CLIC5 exists in two alternative splice variants, a smaller CLIC5A and larger CLIC5B protein. CLIC5A is expressed chiefly in the renal

glomerulus ''Glomerulus'' (; : glomeruli) is a common term used in anatomy to describe globular structures of entwined vessels, fibers, or neurons. ''Glomerulus'' is the diminutive of the Latin ''glomus'', meaning "ball of yarn". ''Glomerulus'' may refer to ...

, specifically in

podocytes Podocytes are cells in Bowman's capsule in the kidneys that wrap around capillaries of the glomerulus. Podocytes make up the epithelial lining of Bowman's capsule, the third layer through which filtration of blood takes place. Bowman's capsule ...

. Within the cell, CLIC5A is localized to the

plasma membrane The cell membrane (also known as the plasma membrane or cytoplasmic membrane, and historically referred to as the plasmalemma) is a biological membrane that separates and protects the interior of a cell from the outside environment (the extr ...

and the

cytosol The cytosol, also known as cytoplasmic matrix or groundplasm, is one of the liquids found inside cells ( intracellular fluid (ICF)). It is separated into compartments by membranes. For example, the mitochondrial matrix separates the mitochondri ...

, and associates and is regulated by the

actin Actin is a family of globular multi-functional proteins that form microfilaments in the cytoskeleton, and the thin filaments in muscle fibrils. It is found in essentially all eukaryotic cells, where it may be present at a concentration of ...

cytoskeleton The cytoskeleton is a complex, dynamic network of interlinking protein filaments present in the cytoplasm of all cells, including those of bacteria and archaea. In eukaryotes, it extends from the cell nucleus to the cell membrane and is compos ...

. CLIC5A can form ion channels in vitro and its channel activity is regulated by

, though measurement of its chloride conductance ''in vitro'' suggests that CLIC5A is equally selective for cations and anions. Even so, the function of CLICs as bona fide ion channels is controversial and has been disputed.

Function

Although chloride intracellular channel (CLIC) proteins were thought to be involved in ion transport in subcellular compartments, their actual functions suggest their role in diverse cellular and physiological functions including

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 ...

and

angiogenesis Angiogenesis is the physiological process through which new blood vessels form from pre-existing vessels, formed in the earlier stage of vasculogenesis. Angiogenesis continues the growth of the vasculature mainly by processes of sprouting and ...

in CLIC1. CLIC5A, through its interactions with the

small GTPase Small GTPases (), also known as small G-proteins, are a family of hydrolase enzymes that can bind and hydrolyze guanosine triphosphate (GTP). They are a type of G-protein found in the cytosol that are homologous to the alpha subunit of heterotrim ...

Rac1 Ras-related C3 botulinum toxin substrate 1, is a protein that in humans is encoded by the ''RAC1'' gene. This gene can produce a variety of alternatively spliced versions of the Rac1 protein, which appear to carry out different functions. Func ...

, induces the phosphorylation of

ezrin Ezrin also known as cytovillin or villin-2 is a protein that in humans is encoded by the ''EZR'' gene. Structure The N-terminus of ezrin contains a FERM domain which is further subdivided into three subdomains. The C-terminus contains an ...

-moeisin-radixin (ERM) proteins and localized production of the

phosphoinositide Phosphatidylinositol or inositol phospholipid is a biomolecule. It was initially called "inosite" when it was discovered by Léon Maquenne and Johann Joseph von Scherer in the late 19th century. It was discovered in bacteria but later also found ...

phosphatidylinositol-4,5-bisphosphate. These two events activate ezrin, enabling it to couple transmembrane proteins to the actin cytoskeleton, which could represent a mechanism by which

podocyte foot processes Podocytes are cells in Bowman's capsule in the kidneys that wrap around capillaries of the glomerulus. Podocytes make up the epithelial lining of Bowman's capsule, the third layer through which filtration of blood takes place. Bowman's capsule ...

form to enable renal filtration.

Clinical relevance

Two human families with loss-of-function CLIC5 mutations have been reported, with a total of 5 affected individuals. CLIC5 deficiency results in progressive hearing loss by the second decade, vestibular abnormalities, and kidney dysfunction. CLIC5A deficiency in mouse models potentiates glomerular injury in hypertension. In these mice, podocyte foot processes were also more sparse and disperse than in wild-type mice.

References

External links

* * Ion channels {{gene-6-stub

Expression and localization

Function

Clinical relevance

See also

References

Further reading

External links