Cochlin is a
protein that in humans is encoded by the ''COCH''
gene.
It is an extracellular matrix (ECM) protein highly abundant in the cochlea and vestibule of the inner ear, constituting the major non-collagen component of the ECM of the inner ear.
The protein is highly conserved in human, mouse, and chicken, showing 94% and 79% amino acid identity of human to mouse and chicken sequences, respectively.
Structure
Cochlin contains three protein domains: an N-terminal
LCCL domain
In molecular biology, the LCCL domain is a protein domain which has been named after several well-characterised proteins that were found to contain it, namely Limulus clotting factor C, Cochlin (Coch-5b2) and Lgl1 ( CRISPLD2). It is an about 100 a ...
, and two copies of
Von Willebrand factor type A domains.
Function
The gene is expressed in spindle-shaped cells located along nerve fibers between the auditory ganglion and sensory epithelium. These cells accompany
neurites at the
habenula perforata
In neuroanatomy, habenula (diminutive of Latin ''habena'' meaning rein) originally denoted the stalk of the pineal gland (pineal habenula; pedunculus of pineal body), but gradually came to refer to a neighboring group of nerve cells with which the ...
, the opening through which neurites extend to innervate hair cells. This and the pattern of expression of this gene in chicken inner ear paralleled the histologic findings of
acidophilic
Acidophiles or acidophilic organisms are those that thrive under highly acidic conditions (usually at pH 5.0 or below). These organisms can be found in different branches of the tree of life, including Archaea, Bacteria,Becker, A.Types of Bacteria ...
deposits, consistent with
mucopolysaccharide ground substance, in temporal bones from
DFNA9 (autosomal dominant nonsyndromic sensorineural deafness 9) patients. Mutations that cause DFNA9 have been reported in this gene.
Cochlin has been identified in the
trabecular meshwork (TM) of
glaucoma patients, but not in healthy controls. The TM is a filter like area of tissue in the eye; cochlin may have a role in cell adhesion, mechanosensation, and modulation of the TM filter.
It is also expressed in
follicular dendritic cells in spleen and
lymph node
A lymph node, or lymph gland, is a kidney-shaped organ of the lymphatic system and the adaptive immune system. A large number of lymph nodes are linked throughout the body by the lymphatic vessels. They are major sites of lymphocytes that inclu ...
s. Here, cochlin is cleaved by
aggrecanase
Aggrecanases are extracellular proteolytic enzymes that are members of the ADAMTS (A Disintegrin And Metalloprotease with Thrombospondin Motifs) family. Aggrecanases act on large proteoglycans known as aggrecans, which are components of connective ...
s and secreted into blood circulation during inflammation, contributing to the antibacterial
innate immune response
The innate, or nonspecific, immune system is one of the two main immunity strategies (the other being the adaptive immune system) in vertebrates. The innate immune system is an older evolutionary defense strategy, relatively speaking, and is the ...
.
References
Further reading
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
{{InterPro content, IPR030743
Extracellular matrix proteins