DNAJC5
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DnaJ homolog subfamily C member 5, also known as cysteine string protein or CSP is a
protein Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, res ...
, that in humans encoded by the ''DNAJC5''
gene In biology, the word gene (from , ; "... Wilhelm Johannsen coined the word gene to describe the Mendelian units of heredity..." meaning ''generation'' or ''birth'' or ''gender'') can have several different meanings. The Mendelian gene is a b ...
. It was first described in 1990.


Gene

In humans, the gene is located on the long arm of
chromosome 20 Chromosome 20 is one of the 23 pairs of chromosomes in humans. Chromosome 20 spans around 66 million base pairs (the building material of DNA) and represents between 2 and 2.5 percent of the total DNA in cells. Chromosome 20 was fully sequenced i ...
(20q13.33) on the Watson (positive strand). The gene is 40,867 bases in length and the encoded
protein Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, res ...
has 198
amino acid Amino acids are organic compounds that contain both amino and carboxylic acid functional groups. Although hundreds of amino acids exist in nature, by far the most important are the alpha-amino acids, which comprise proteins. Only 22 alpha a ...
s with a predicted molecular weight of 22.149 kilo
Dalton Dalton may refer to: Science * Dalton (crater), a lunar crater * Dalton (program), chemistry software * Dalton (unit) (Da), the atomic mass unit * John Dalton, chemist, physicist and meteorologist Entertainment * Dalton (Buffyverse), minor ch ...
s (kDa). The weight of the mature protein is 34kDa. This gene is highly conserved and found both in
invertebrate Invertebrates are a paraphyletic group of animals that neither possess nor develop a vertebral column (commonly known as a ''backbone'' or ''spine''), derived from the notochord. This is a grouping including all animals apart from the chordate ...
s and
vertebrate Vertebrates () comprise all animal taxa within the subphylum Vertebrata () (chordates with backbones), including all mammals, birds, reptiles, amphibians, and fish. Vertebrates represent the overwhelming majority of the phylum Chordata, with c ...
s. In humans, a pseudogene of this gene is located on the short arm of
chromosome 8 Chromosome 8 is one of the 23 pairs of chromosomes in humans. People normally have two copies of this chromosome. Chromosome 8 spans about 145 million base pairs (the building material of DNA) and represents between 4.5 and 5.0% of the total DNA ...
.


Structure

The organisation of the protein is as follows: * an N-terminus phosphorylation site for
protein kinase A In cell biology, protein kinase A (PKA) is a family of enzymes whose activity is dependent on cellular levels of cyclic AMP (cAMP). PKA is also known as cAMP-dependent protein kinase (). PKA has several functions in the cell, including regulatio ...
* a J domain (~70 amino acids) * a linker region * a cysteine motif consisting of 13–15 cysteines within a stretch of 25 amino acids. It is heavily palmitoylated in the cysteine string motif. * a less conserved
C-terminal The C-terminus (also known as the carboxyl-terminus, carboxy-terminus, C-terminal tail, C-terminal end, or COOH-terminus) is the end of an amino acid chain (protein or polypeptide), terminated by a free carboxyl group (-COOH). When the protein is ...
domain


Tissue distribution

This protein is abundant in neural tissue and displays a characteristic localization to synaptic and
clathrin Clathrin is a protein that plays a major role in the formation of coated vesicles. Clathrin was first isolated and named by Barbara Pearse in 1976. It forms a triskelion shape composed of three clathrin heavy chains and three light chains. When ...
coated vesicles. It is also found on secretory vesicles in endocrine, neuroendocrine and exocrine cells. This protein makes up ~1% of the protein content of the
synaptic vesicle In a neuron, synaptic vesicles (or neurotransmitter vesicles) store various neurotransmitters that are released at the synapse. The release is regulated by a voltage-dependent calcium channel. Vesicles are essential for propagating nerve impulse ...
s. DNAJC5 appears to have a role in stimulated exocytosis.


Function

The encoded protein is a member of the J protein family. These proteins function in many cellular processes by regulating the ATPase activity of 70 kDa
heat shock protein Heat shock proteins (HSP) are a family of proteins produced by cells in response to exposure to stressful conditions. They were first described in relation to heat shock, but are now known to also be expressed during other stresses including expo ...
s (
Hsp70 The 70 kilodalton heat shock proteins (Hsp70s or DnaK) are a family of conserved ubiquitously expressed heat shock proteins. Proteins with similar structure exist in virtually all living organisms. Intracellularly localized Hsp70s are an import ...
). DNAJC5 is a
guanine nucleotide exchange factor Guanine nucleotide exchange factors (GEFs) are proteins or protein domains that activate monomeric GTPases by stimulating the release of guanosine diphosphate (GDP) to allow binding of guanosine triphosphate (GTP). A variety of unrelated struc ...
for Gα proteins. CSPα plays a role in membrane
trafficking Smuggling is the illegal transportation of objects, substances, information or people, such as out of a house or buildings, into a prison, or across an international border, in violation of applicable laws or other regulations. There are various ...
and
protein folding Protein folding is the physical process by which a protein chain is translated to its native three-dimensional structure, typically a "folded" conformation by which the protein becomes biologically functional. Via an expeditious and reproduc ...
, and has been shown to have anti-
neurodegenerative A neurodegenerative disease is caused by the progressive loss of structure or function of neurons, in the process known as neurodegeneration. Such neuronal damage may ultimately involve cell death. Neurodegenerative diseases include amyotrophic ...
properties. It is known to play a role in cystic fibrosis and
Huntington's disease Huntington's disease (HD), also known as Huntington's chorea, is a neurodegenerative disease that is mostly inherited. The earliest symptoms are often subtle problems with mood or mental abilities. A general lack of coordination and an uns ...
. This protein has been proposed as a key element of the synaptic molecular machinery devoted to the rescue of synaptic proteins that have been unfolded by activity dependent stress. Syntaxin 1A, a plasma membrane
SNARE SNARE proteins – " SNAP REceptor" – are a large protein family consisting of at least 24 members in yeasts, more than 60 members in mammalian cells, and some numbers in plants. The primary role of SNARE proteins is to mediate vesicle f ...
(soluble N-ethylmaleimide-sensitive factor attachment protein receptor) critical for neurotransmission, forms a complex with CSPα, a
G protein G proteins, also known as guanine nucleotide-binding proteins, are a family of proteins that act as molecular switches inside cells, and are involved in transmitting signals from a variety of stimuli outside a cell to its interior. Their a ...
and an
N-type calcium channel N-type calcium channels also called Cav2.2 channels are voltage gated calcium channels that are localized primarily on the nerve terminals and dendrites as well as neuroendocrine cells. The calcium N-channel consists of several subunits: the prima ...
.
Huntingtin Huntingtin (Htt) is the protein coded for in humans by the ''HTT'' gene, also known as the ''IT15'' ("interesting transcript 15") gene. Mutated ''HTT'' is the cause of Huntington's disease (HD), and has been investigated for this role and also fo ...
may be able displace both syntaxin 1A and CSPα from N-type channels. CSP interacts with the calcium sensor protein synaptotagmin 9 via its linker domain. Huntingtin-interacting protein 14, a palmitoyl transferase, is required for exocytosis and targeting of CSP to synaptic vesicles. The palmitoyl residues are transferred to the cysteine residues. If these resides are mutated membrane targeting is reduced or lost. The rat CSP forms a complex with Sgt (
SGTA Small glutamine-rich tetratricopeptide repeat-containing protein alpha is a protein that in humans is encoded by the ''SGTA'' gene. ''SGTA'' orthologs have also been identified in several mammals for which complete genome data are available. Fu ...
) and Hsc70 (
HSPA8 Heat shock 70 kDa protein 8 also known as heat shock cognate 71 kDa protein or Hsc70 or Hsp73 is a heat shock protein that in humans is encoded by the ''HSPA8'' gene on chromosome 11. As a member of the heat shock protein 70 family and a chaperon ...
) located on the
synaptic vesicle In a neuron, synaptic vesicles (or neurotransmitter vesicles) store various neurotransmitters that are released at the synapse. The release is regulated by a voltage-dependent calcium channel. Vesicles are essential for propagating nerve impulse ...
surface. This complex functions as an ATP-dependent chaperone that reactivates denatured substrates. Furthermore, the Csp/Sgt/Hsc70 complex appears to be important for maintenance of normal synapses. Its expression may be increased with the use of
lithium Lithium (from el, λίθος, lithos, lit=stone) is a chemical element with the symbol Li and atomic number 3. It is a soft, silvery-white alkali metal. Under standard conditions, it is the least dense metal and the least dense solid ...
.
Quercetin Quercetin is a plant flavonol from the flavonoid group of polyphenols. It is found in many fruits, vegetables, leaves, seeds, and grains; capers, red onions, and kale are common foods containing appreciable amounts of it. It has a bitter flavor ...
promotes formation of stable CSPα-CSPα dimers. Cysteine-string protein increases the calcium sensitivity of neurotransmitter exocytosis.


Interactions

DNAJC5 has been shown to
interact Advocates for Informed Choice, dba interACT or interACT Advocates for Intersex Youth, is a 501(c)(3) nonprofit organization using innovative strategies to advocate for the legal and human rights of children with intersex traits. The organizati ...
with the
cystic fibrosis transmembrane conductance regulator Cystic fibrosis transmembrane conductance regulator (CFTR) is a membrane protein and anion channel in vertebrates that is encoded by the ''CFTR'' gene. Geneticist Lap-Chee Tsui and his team identified the CFTR gene in 1989 as the gene linked wi ...
.


Clinical significance

Mutations in this gene may cause
neuronal ceroid lipofuscinosis Neuronal ceroid lipofuscinosis is the general name for a family of at least eight genetically separate neurodegenerative lysosomal storage diseases that result from excessive accumulation of lipopigments ( lipofuscin) in the body's tissues. These ...
.


References


Further reading

* * * * * * * * * * * * * * * * * *


External links


GeneReviews/NCBI/NIH/UW entry on Neuronal Ceroid-Lipofuscinosis
{{Chaperones Heat shock proteins Co-chaperones