title: Biosynthesis of proTRH-derived peptides in prohormone convertase 1 and 2 knockout mice.
abstract: Prohormone convertases (PCs) 1 and 2 are the primary endoproteases involved in the post-translational processing of proThyrotropin Releasing Hormone (proTRH) to give rise to TRH and other proposed biologically active non-TRH peptides. Previous evidence suggests that PC1 is responsible for most proTRH cleavage events. Here, we used the PC1 and PC2 knockout (KO) mouse models to examine the effects of PC1 or PC2 loss on proTRH processing. The PC1KO mouse presented a decrease in five proTRH-derived peptides, whereas the PC2KO mouse showed only lesser reduction in three TRH (Gln-His-Pro), TRH-Gly (Gln-His-Pro-Gly), and the short forms preproTRH(178-184) (pFQ(7)) and preproTRH(186-199) (pSE(14)) of pFE(22) (preproTRH(178-199)). Also, PC1KO and not PC2KO showed a decrease in pEH(24) indicating that PC1 is more important in generating this peptide in the mouse, which differs from previous studies using rat proTRH. Furthermore, downstream effects on thyroid hormone levels were evident in PC1KO mice, but not PC2KO mice suggesting that PC1 plays the more critical role in producing bioactive hypophysiotropic TRH. Yet loss of PC1 did not abolish TRH entirely indicating a complementary action for both enzymes in the normal processing of proTRH. We also show that PC2 alone is responsible for catalyzing the conversion of pFE(22) to pFQ(7) and pSE(14), all peptides implicated in regulation of suckling-induced prolactin release. Collectively, results characterize the specific roles of PC1 and PC2 in proTRH processing in vivo.
authors.affiliation: Division of Endocrinology, Department of Medicine, The Warren Alpert Medical School of Brown University/Rhode Island Hospital, Providence, RI 02903, USA.
authors.forename: Nicole E
authors.initials: NE
authors.lastname: Cyr
authors.forename: Ronald C
authors.initials: RC
authors.lastname: Stuart
authors.forename: Xiaorong
authors.initials: X
authors.lastname: Zhu
authors.forename: Donald F
authors.initials: DF
authors.lastname: Steiner
authors.forename: Eduardo A
authors.initials: EA
authors.lastname: Nillni
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D051379:Mice; D018345:Mice, Knockout; D008969:Molecular Sequence Data; D010286:Paraventricular Hypothalamic Nucleus / Q000378:metabolism; D010446:Peptide Fragments / Q000096:biosynthesis*; D045664:Proprotein Convertase 1 / Q000172:deficiency / Q000235:genetics*; D045706:Proprotein Convertase 2 / Q000172:deficiency / Q000235:genetics*; D011498:Protein Precursors / Q000096:biosynthesis*; D017386:Sequence Homology, Amino Acid; D013973:Thyrotropin-Releasing Hormone / Q000096:biosynthesis*; D014284:Triiodothyronine / Q000096:biosynthesis
chemical_list: D010446:Peptide Fragments; D011498:Protein Precursors; D014284:Triiodothyronine; D013973:Thyrotropin-Releasing Hormone; D045664:Proprotein Convertase 1; D045706:Proprotein Convertase 2