Sacsin also known as DnaJ homolog subfamily C member 29 (DNAJC29) 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 ''SACS''
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 ...
.
Sacsin is a
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 and play crucial roles in the development of can ...
co-chaperone
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 stimulatio ...
.
Function
This gene consists of nine exons including a gigantic exon spanning more than 12.8k bp. It encodes the sacsin protein, which includes a UBQ region at the
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 ...
, a
HEPN domain at the
C-terminus
The C-terminus (also known as the carboxyl-terminus, carboxy-terminus, C-terminal tail, carboxy tail, C-terminal end, or COOH-terminus) is the end of an amino acid chain (protein
Proteins are large biomolecules and macromolecules that comp ...
and a
DnaJ
In molecular biology, chaperone DnaJ, also known as Hsp40 (heat shock protein 40 kDa), is a molecular chaperone protein. It is expressed in a wide variety of organisms from bacteria to humans.
Function
Molecular chaperones are a diverse family ...
region upstream of the HEPN domain. This modular protein is essential for normal mitochondrial network organization.
The gene is highly expressed in the central nervous system, also found in skin, skeletal muscles and at low levels in the pancreas. Mutations in this gene result in autosomal recessive spastic ataxia of Charlevoix-Saguenay (ARSACS), a neurodegenerative disorder characterized by early-onset
cerebellar ataxia
Cerebellar ataxia is a form of ataxia originating in the cerebellum. Non-progressive congenital ataxia (NPCA) is a classical presentation of cerebral ataxias.
Cerebellar ataxia can occur as a result of many diseases and may present with symptoms ...
with
spasticity
Spasticity () is a feature of altered skeletal muscle performance with a combination of paralysis, increased tendon reflex activity, and hypertonia. It is also colloquially referred to as an unusual "tightness", stiffness, or "pull" of muscles. ...
and
peripheral neuropathy
Peripheral neuropathy, often shortened to neuropathy, refers to damage or disease affecting the nerves. Damage to nerves may impair sensation, movement, gland function, and/or organ function depending on which nerve fibers are affected. Neuropa ...
.
Clinical significance
Autosomal recessive spastic ataxia of Charlevoix-Saguenay (ARSACS) is a very rare
neurodegenerative
A neurodegenerative disease is caused by the progressive loss of neurons, in the process known as neurodegeneration. Neuronal damage may also ultimately result in their death. Neurodegenerative diseases include amyotrophic lateral sclerosis, mul ...
genetic disorder that results from mutations in the gene that produces Sacsin. Afflicted persons suffer from loss of balance, loss of muscle control and spasticity.
References
Further reading
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External links
GeneReviews/NCBI/NIH/UW entry on ARSACS - Autosomal Recessive Spastic Ataxia of Charlevoix-Saguenay OMIM entries on ARSACS - Autosomal Recessive Spastic Ataxia of Charlevoix-Saguenay
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Co-chaperones