Alternative titles; symbolsSENESCENCE MARKER PROTEIN 30; SMP30HGNC Approved Gene Symbol: RGNCytogenetic location: Xp11.3 Genomic coordinates (GRCh38): X:47,0...
Alternative titles; symbols
HGNC Approved Gene Symbol: RGN
Cytogenetic location: Xp11.3 Genomic coordinates (GRCh38): X:47,078,413-47,093,312 (from NCBI)
▼ Cloning and Expression
During a survey of age-associated changes in the soluble proteins from rat livers, Fujita et al. (1992) isolated a novel 30-kD protein, Smp30, which did not show a gender difference in age-associated decrease. Fujita et al. (1992) determined that Smp30 is preferentially localized in hepatocytes and renal proximal tubular epithelial cells of rats. Smp30 is identical to the calcium-binding protein called regucalcin, which was isolated from the liver of rats by Shimokawa and Yamaguchi (1993).
Using rat Smp30 cDNA as a probe, Fujita et al. (1995) obtained a cDNA clone encoding the human homolog from a human liver cDNA library. The cDNA encodes a predicted 299-amino acid protein that shows 88.9% sequence similarity with the rat protein.
▼ Gene Function
To determine how SMP30 functions, Fujita (1999) transfected HepG2 cells with human SMP30 cDNA so that the cells stably expressed large amounts of SMP30. When cytosolic calcium ion was elevated, such cells exhibited an augmented efflux of calcium ions because of increased plasma membrane pumping activity. Fujita (1999) concluded that SMP30 plays an important role in calcium homeostasis. Calcium is a second messenger for signal transduction. Fujita (1999) suggested that the age-associated decrease in SMP30 may alter the signaling system and increase the tissue susceptibility to harmful stimuli.
Kondo et al. (2006) found Smp30 purified from rat liver had lactonase activity toward various aldonolactones and required Zn(2+) or Mn(2+) as a cofactor. The lactonase reaction with L-gulono gamma-lactone is the penultimate step in L-ascorbic acid biosynthesis.
By analysis of rodent-human somatic cell hybrids, Fujita et al. (1995) mapped the SMP30 gene to Xp11.2-q11.2.
▼ Animal Model
Kondo et al. (2006) found that Smp30-null mice fed a vitamin C-deficient diet displayed symptoms of scurvy, such as bone fracture and rachitic rosary, and died within 135 days of starting the diet. The L-ascorbic acid levels in their livers and kidneys at the time of death were less than 1.6% of those in wildtype control mice.