SPTLC1
Domain
The transmembrane domain is involved in the interaction with ORMDL3.
Function
Component of the serine palmitoyltransferase multisubunit enzyme (SPT) that catalyzes the initial and rate-limiting step in sphingolipid biosynthesis by condensing L-serine and activated acyl-CoA (most commonly palmitoyl-CoA) to form long-chain bases. The SPT complex is also composed of SPTLC2 or SPTLC3 and SPTSSA or SPTSSB. Within this complex, the heterodimer with SPTLC2 or SPTLC3 forms the catalytic core (PubMed:19416851, PubMed:33558762, PubMed:36170811). The composition of the serine palmitoyltransferase (SPT) complex determines the substrate preference (PubMed:19416851, PubMed:33558762). The SPTLC1-SPTLC2-SPTSSA complex shows a strong preference for C16-CoA substrate, while the SPTLC1-SPTLC3-SPTSSA isozyme uses both C14-CoA and C16-CoA as substrates, with a slight preference for C14-CoA (PubMed:19416851, PubMed:19648650). The SPTLC1-SPTLC2-SPTSSB complex shows a strong preference for C18-CoA substrate, while the SPTLC1-SPTLC3-SPTSSB isozyme displays an ability to use a broader range of acyl-CoAs, without apparent preference (PubMed:19416851, PubMed:19648650, PubMed:33558761, PubMed:33558762). Required for adipocyte cell viability and metabolic homeostasis (By similarity).
Involvement in disease
Amyotrophic lateral sclerosis 27, juvenile
ALS27
A form of amyotrophic lateral sclerosis, a neurodegenerative disorder affecting upper motor neurons in the brain and lower motor neurons in the brain stem and spinal cord, resulting in fatal paralysis. Sensory abnormalities are absent. The pathologic hallmarks of the disease include pallor of the corticospinal tract due to loss of motor neurons, presence of ubiquitin-positive inclusions within surviving motor neurons, and deposition of pathologic aggregates. The etiology of amyotrophic lateral sclerosis is likely to be multifactorial, involving both genetic and environmental factors. The disease is inherited in 5-10% of the cases. ALS27 is an autosomal dominant form manifesting as toe walking and gait abnormalities in early childhood.
None
The disease is caused by variants affecting the gene represented in this entry. Variants associated with ALS27 tend to disrupt the normal homeostatic regulation of serine palmitoyltransferase (SPT) by ORMDL proteins, resulting in up-regulated SPT activity and elevated levels of canonical SPT products.
Neuropathy, hereditary sensory and autonomic, 1A
HSAN1A
A form of hereditary sensory and autonomic neuropathy, a genetically and clinically heterogeneous group of disorders characterized by degeneration of dorsal root and autonomic ganglion cells, and by prominent sensory abnormalities with a variable degree of motor and autonomic dysfunction. The neurological phenotype is often complicated by severe infections, osteomyelitis, and amputations. HSAN1A is an autosomal dominant axonal form with onset in the second or third decades. Initial symptoms are loss of pain, touch, heat, and cold sensation over the feet, followed by distal muscle wasting and weakness. Loss of pain sensation leads to chronic skin ulcers and distal amputations.
None
The disease is caused by variants affecting the gene represented in this entry. Variants associated with HSAN1A tend to increase serine palmitoyltransferase (SPT) usage of alanine or glycine rather than serine, resulting in deoxysphingolipid synthesis. Deoxysphingolipids cannot be efficiently degraded by the cell machinery and cause cell toxicity.
Pathway
Lipid metabolism; sphingolipid metabolism.
Post-translational modifications
Phosphorylation at Tyr-164 inhibits activity and promotes cell survival.
Sequence Similarities
Belongs to the class-II pyridoxal-phosphate-dependent aminotransferase family.
Tissue Specificity
Widely expressed. Not detected in small intestine.
Cellular localization
- Endoplasmic reticulum membrane
- Single-pass membrane protein
Alternative names
LCB1, SPTLC1, Serine palmitoyltransferase 1, Long chain base biosynthesis protein 1, Serine-palmitoyl-CoA transferase 1, LCB 1, SPT 1, SPT1