| DNAJC5 | |||||||||||||||||||||||||||||||||||||||||||||||||||
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| Aliases | DNAJC5 , CLN4, CLN4B, CSP, DNAJC5A, NCL, mir-941-2, mir-941-3, mir-941-4, mir-941-5, DnaJ heat shock protein family (Hsp40) member C5 | ||||||||||||||||||||||||||||||||||||||||||||||||||
| External IDs | OMIM: 611203 MGI: 892995 HomoloGene: 9631 GeneCards: DNAJC5 | ||||||||||||||||||||||||||||||||||||||||||||||||||
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DnaJ homolog subfamily C member 5, also known as cysteine string protein or CSP is a protein, that in humans encoded by the DNAJC5 gene. [5] It was first described in 1990. [6]
In humans, the gene is located on the long arm of chromosome 20 (20q13.33) on the Watson (positive strand). The gene is 40,867 bases in length and the encoded protein has 198 amino acids with a predicted molecular weight of 22.149 kilodaltons (kDa). The weight of the mature protein is 34 kDa.
This gene is highly conserved and found both in invertebrates and vertebrates. In humans, a pseudogene of this gene is located on the short arm of chromosome 8.
The organisation of the protein is as follows: [7]
This protein is abundant in neural tissue and displays a characteristic localization to synaptic and clathrin 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 vesicles. [8] DNAJC5 appears to have a role in stimulated exocytosis. [9]
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 proteins (Hsp70). DNAJC5 is a guanine nucleotide exchange factor for Gα proteins. [10] CSPα plays a role in membrane trafficking and protein folding, and has been shown to have anti-neurodegenerative properties. It is known to play a role in cystic fibrosis and Huntington's disease. [5]
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. [11] [12] Syntaxin 1A, a plasma membrane SNARE (soluble N-ethylmaleimide-sensitive factor attachment protein receptor) critical for neurotransmission, forms a complex with CSPα, a G protein and an N-type calcium channel. Huntingtin may be able displace both syntaxin 1A and CSPα from N-type channels. [13] CSP interacts with the calcium sensor protein synaptotagmin 9 via its linker domain. [14]
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. [15] The rat CSP forms a complex with Sgt (SGTA) and Hsc70 (HSPA8) located on the synaptic vesicle 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. [7]
Its expression may be increased with the use of lithium. [16] Quercetin promotes formation of stable CSPα-CSPα dimers. [17]
Cysteine-string protein increases the calcium sensitivity of neurotransmitter exocytosis. [18]
DNAJC5 has been shown to interact with the cystic fibrosis transmembrane conductance regulator. [19]
Mutations in this gene may cause neuronal ceroid lipofuscinosis. [20]
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 lipopigments are made up of fats and proteins. Their name comes from the word stem "lipo-", which is a variation on lipid, and from the term "pigment", used because the substances take on a greenish-yellow color when viewed under an ultraviolet light microscope. These lipofuscin materials build up in neuronal cells and many organs, including the liver, spleen, myocardium, and kidneys.
SNARE proteins – "SNAPREceptors" – 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 the fusion of vesicles with the target membrane; this notably mediates exocytosis, but can also mediate the fusion of vesicles with membrane-bound compartments. The best studied SNAREs are those that mediate the release of synaptic vesicles containing neurotransmitters in neurons. These neuronal SNAREs are the targets of the neurotoxins responsible for botulism and tetanus produced by certain bacteria.
Synaptosomal-Associated Protein, 25kDa (SNAP-25) is a Target Soluble NSF (N-ethylmaleimide-sensitive factor) Attachment Protein Receptor (t-SNARE) protein encoded by the SNAP25 gene found on chromosome 20p12.2 in humans. SNAP-25 is a component of the trans-SNARE complex, which accounts for membrane fusion specificity and directly executes fusion by forming a tight complex that brings the synaptic vesicle and plasma membranes together.
Co-chaperones are proteins that assist chaperones in protein folding and other functions. Co-chaperones are the non-client binding molecules that assist in protein folding mediated by Hsp70 and Hsp90. They are particularly essential in stimulation of the ATPase activity of these chaperone proteins. There are a great number of different co-chaperones however based on their domain structure most of them fall into two groups: J-domain proteins and tetratricopeptide repeats (TPR).
Peripheral plasma membrane protein CASK is a protein that in humans is encoded by the CASK gene. This gene is also known by several other names: CMG 2, calcium/calmodulin-dependent serine protein kinase 3 and membrane-associated guanylate kinase 2. CASK gene mutations are the cause of XL-ID with or without nystagmus and MICPCH, an X-linked neurological disorder.
Syntaxin-binding protein 1 is a protein that in humans is encoded by the STXBP1 gene. This gene encodes a syntaxin-binding protein. The encoded protein appears to play a role in release of neurotransmitters via regulation of syntaxin, a transmembrane attachment protein receptor. Mutations in this gene have been associated with neurological disorders including epilepsy, intellectual disability, and movement disorders.
Calcium/calmodulin-dependent protein kinase type 1 is an enzyme that in humans is encoded by the CAMK1 gene.
Complexin-2 is a protein that in humans is encoded by the CPLX2 gene.
Regulating synaptic membrane exocytosis protein 1 is a protein that in humans is encoded by the RIMS1 gene.
Rabphilin-3A is a protein that in humans is encoded by the RPH3A gene. It contains two C2 domains and binds calcium ions at low micromolar concentration. Rabphilin was shown to regulate neurotransmitter release in hippocampal neurons after neurons had an increased synaptic activity and their release rate was depressed.
Ceroid-lipofuscinosis neuronal protein 6 is a protein that in humans is encoded by the CLN6 gene.
Synaptotagmin-like protein 4 is a protein that in humans is encoded by the SYTL4 gene.
Calcium-dependent secretion activator 1 is a protein that in humans is encoded by the CADPS gene.
Protein CLN8 is a protein that in humans is encoded by the CLN8 gene.
Calcium-dependent secretion activator 2 is a protein that in humans is encoded by the CADPS2 gene.
Synaptic vesicle glycoprotein 2B is a protein that in humans is encoded by the SV2B gene.
Palmitoyl-protein thioesterase 1 (PPT-1), also known as palmitoyl-protein hydrolase 1, is an enzyme that in humans is encoded by the PPT1 gene.
Major facilitator superfamily domain containing 8 also called MFSD8 is a protein that in humans is encoded by the MFSD8 gene. MFSD8 is an atypical SLC, thus a predicted SLC transporter. It clusters phylogenetically to the Atypical MFS Transporter family 2 (AMTF2).
Synapsin II is the collective name for synapsin IIa and synapsin IIb, two nearly identical phosphoproteins in the synapsin family that in humans are encoded by the SYN2 gene. Synapsins associate as endogenous substrates to the surface of synaptic vesicles and act as key modulators in neurotransmitter release across the presynaptic membrane of axonal neurons in the nervous system.
Kufs disease is one of many diseases categorized under a disorder known as neuronal ceroid lipofuscinosis (NCLs) or Batten disease. NCLs are broadly described to create problems with vision, movement and cognitive function. Among all NCLs diseases, Kufs is the only one that does not affect vision, and although this is a distinguishing factor of Kufs, NCLs are typically differentiated by the age at which they appear in a patient
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