Species-specific alternative splicing generates a catalytically inactive form of human hormone-sensitive lipase.
Hormone-sensitive lipase (HSL) catalyses the rate-limiting step of adipose tissue lipolysis. The enzyme is also expressed in steroidogenic tissues, mammary gland, muscle tissues and macrophages. A novel HSL mRNA termed hHSL-S, 228 bp shorter than the full-length HSL mRNA, was detected in human adipocytes. hHSL-S mRNA results from the in-frame skipping of exon 6, which encodes the serine residue of the catalytic triad. The corresponding 80 kDa protein was identified in human adipocytes after immunoprecipitation. The truncated protein expressed in COS cells showed neither lipase nor esterase activity but was phosphorylated by cAMP-dependent protein kinase. hHSL-S mRNA was found in all human tissues expressing HSL, except brown adipose tissue from newborns. It represented approx. 20% of total HSL transcripts in human subcutaneous adipocytes. No alternative splicing was detected in other mammals. Human and mouse three-exon HSL minigenes transfected into primate and rodent cell lines reproduced the splicing pattern of the endogenous HSL genes. Analysis of hybrid human/mouse minigenes transfected into human cell lines showed that cis-acting elements responsible for the skipping of human exon 6 were restricted to a 247 bp region including exon 6 and the first 19 nt of intron 6. Moreover, divergence in exonic splicing elements between mouse and human was shown to be critical for the species-specific alternative splicing.
Laurell
H
H
Unité INSERM 317, Institut Louis Bugnard, Faculté de Médecine, Université Paul Sabatier, Toulouse, France.
Grober
J
J
Vindis
C
C
Lacombe
T
T
Dauzats
M
M
Holm
C
C
Langin
D
D
D017398:Alternative Splicing; D000818:Animals; D001483:Base Sequence; D019556:COS Cells; D006528:Carcinoma, Hepatocellular; D002384:Catalysis; D004789:Enzyme Activation / Q000235:genetics; D005822:Genetic Vectors / Q000096:biosynthesis / Q000502:physiology; D006801:Humans; D051379:Mice; D008969:Molecular Sequence Data; D009928:Organ Specificity / Q000235:genetics; D012322:RNA Precursors / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000737:chemistry; D051381:Rats; D013045:Species Specificity; D002787:Sterol Esterase / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D014162:Transfection; D014407:Tumor Cells, Cultured
D012322:RNA Precursors; D012333:RNA, Messenger; D002787:Sterol Esterase