Biosynthesis of the major urinary proteins in mouse liver: A biochemical genetic study

Abstract

By labeling liver protein in vivo with [3H] leucine, the relative biosynthetic rate has been measured for the major urinary proteins (MUPs), three closely related, androgen-regulated proteins that are synthesized in mouse liver, secreted into the bloodstream, and excreted into the urine. In livers from females of strain C57BL/6J, total MUP synthesis represents about 0.6-0.9% of the total protein synthesis; in males and testosterone-treated females of the same strain, synthesis increases to about 3.5-4.0% of the total. This 4- to 6-fold induction of total MUP synthesis is similar to the androgen-mediated increase in MUP-specific messenger RNA reported by others, and indicates that the previously observed 20- to 25-fold induction of total MUP excretion into urine is generated partly at the posttranslational level. By measuring the ratio of synthesis of the individual MUPs, it was determined that the testosterone-mediated change in the pattern of MUP synthesis, indicating nature, of MUPs excreted. A survey of seven inbred mouse strains revealed polymorphism for the rate of total MUP synthesis in untreated females. Two classes could be distinguished on the basis of a 3-to 5-fold difference in the rate. This variation does not correlate with variation at Mup-a, a locus that controls the ratio of the three MUPs in urine from androgen-induced mice. These findings are consistent with the notion that MUP expression is controlled by a variety of independently assorting genes.

The pioneer translation initiation complex is functionally distinct from but structurally overlaps with the steady-state translation initiation complex

“…Proteins before or after IP were electrophoresed in polyacrylamide (5%-12%), transferred to HyBond ECL nitrocellulose (Amersham), and probed with antibody against CBP80, eIF4E (Santa Cruz), eIF4GI (Bushell et al 2000), eIF2␣ (Santa Cruz), eIF3 (Etchison et al 1982), PABP1 (Gorlach et al 1994), PABP2 (Krause et al 1994), 4E-BP1 (Gingras et al 1998), one of the Upf proteins (Ishigaki et al 2001), HA (Roche), Penta-His (QIAGEN), calnexin (StressGen), or MUP (Berger and Szoka 1981). Reactivity to each antibody was detected using horseradish peroxidaseconjugated donkey ␣-rabbit (Amersham), sheep ␣-mouse (Amersham), donkey ␣-goat (Amersham), or rabbit ␣-rat antibody (Sigma).…”

Cultured hepatocytes from mouse strains expressing high and low levels of the fourth component of complement differ in rate of synthesis of the protein.

“…Age-and sex-related expression of liver proteins is subject to a variety of control mechanisms, including transcriptional and post-translational regulation (17,18). In the studies reported here, we wished to determine whether C4 expression is subject to genetic regulation at the level of protein synthesis.…”

Identification of MUP1 as a Regulator for Glucose and Lipid Metabolism in Mice

“…The liver secretes a variety of proteins, including insulin likegrowth factor-1 (IGF-1), insulin-like growth factor-binding proteins, fibroblast growth factor-21 (FGF-21) and major urinary proteins (MUPs) (2)(3)(4)(5)(6). Insulin-like growth factor-binding proteins and FGF-21 have been well documented to regulate multiple aspects of glucose and lipid metabolism in animals (2,3,7).…”

“…Comparative genomic analyses identify nine MUP genes in rats and a single MUP gene in other mammals (10). MUP1 (ϳ18 kDa in mass) is abundantly expressed in hepatocytes (3.5-4% of total protein synthesis) and secreted into the bloodstream (6,12). MUP1 binds via its central hydrophobic pocket to lipophilic molecules, including volatile pheromones (small odorant molecules) (5,13).…”