Isoprenylation is required for the processing of the lamin A precursor.
The nuclear lamina proteins, prelamin A, lamin B, and a 70-kD lamina-associated protein, are posttranslationally modified by a metabolite derived from mevalonate. This modification can be inhibited by treatment with (3-R,S)-3-fluoromevalonate, demonstrating that it is isoprenoid in nature. We have examined the association between isoprenoid metabolism and processing of the lamin A precursor in human and hamster cells. Inhibition of 3-hydroxy-3-methylglutaryl coenzyme A reductase by mevinolin (lovastatin) specifically depletes endogenous isoprenoid pools and inhibits the conversion of prelamin A to lamin A. Prelamin A processing is also blocked by mevalonate starvation of Mev-1, a CHO cell line auxotrophic for mevalonate. Moreover, inhibition of prelamin A processing by mevinolin treatment is rapidly reversed by the addition of exogenous mevalonate. Processing of prelamin A is, therefore, dependent on isoprenoid metabolism. Analysis of the conversion of prelamin A to lamin A by two independent methods, immunoprecipitation and two-dimensional nonequilibrium pH gel electrophoresis, demonstrates that a precursor-product relationship exists between prelamin A and lamin A. Analysis of R,S-[5-3H(N)]mevalonate-labeled cells shows that the rate of turnover of the isoprenoid group from prelamin A is comparable to the rate of conversion of prelamin A to lamin A. These results suggest that during the proteolytic maturation of prelamin A, the isoprenylated moiety is lost. A significant difference between prelamin A processing, and that of p21ras and the B-type lamins that undergo isoprenylation-dependent proteolytic maturation, is that the mature form of lamin A is no longer isoprenylated.
Beck
L A
LA
Eleanor Roosevelt Institute for Cancer Research, Inc., Denver, Colorado 80206.
Hosick
T J
TJ
Sinensky
M
M
D000595:Amino Acid Sequence; D000818:Animals; D002250:Carbon Radioisotopes; D002467:Cell Nucleus / Q000648:ultrastructure; D002478:Cells, Cultured; D015180:Electrophoresis, Gel, Two-Dimensional; D006801:Humans; D007382:Intermediate Filaments / Q000032:analysis; D007700:Kinetics; D034904:Lamin Type A; D034921:Lamin Type B; D034882:Lamins; D008715:Methionine / Q000378:metabolism; D008798:Mevalonic Acid / Q000378:metabolism*; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000378:metabolism*; D011233:Precipitin Tests; D011498:Protein Precursors / Q000378:metabolism*; D011499:Protein Processing, Post-Translational / Q000502:physiology; D013462:Sulfur Radioisotopes
D002250:Carbon Radioisotopes; D034904:Lamin Type A; D034921:Lamin Type B; D034882:Lamins; D009687:Nuclear Proteins; D011498:Protein Precursors; D013462:Sulfur Radioisotopes; D008715:Methionine; D008798:Mevalonic Acid