Microinjected Xenopus oocytes secrete mature, biologically active parathyroid hormone.
Xenopus oocytes have been shown to faithfully translate, process, and secrete a number of secretory proteins after the injection of heterologous mRNAs. The oocyte has the capacity to perform a variety of posttranslational protein modifications but has been reported to be incapable of carrying out certain two-step cleavages which proceed via propeptide intermediates. We examined the ability of the oocyte to process preproPTH after the injection of parathyroid mRNA. Microinjected oocytes secreted material which could be detected in a sensitive cytochemical bioassay for PTH. This activity paralleled that of the PTH standard in the assay and was entirely eliminated by a competitive inhibitor of PTH binding, by preincubation with an anti-PTH antiserum, and by coinjecting oocytes with an oligonucleotide mixture complementary to PTH sequences. Immunoprecipitable proPTH and PTH were present in oocyte homogenates, but oocyte-conditioned medium contained only mature PTH(1-84). We conclude that the Xenopus oocyte is capable of accurately processing preproPTH to the mature secretory form of the peptide.
Ikeda
K
K
Department of Internal Medicine, Yale University, New Haven, Connecticut 06510.
Posillico
J T
JT
Boyle
M B
MB
Webb
A C
AC
Brown
E M
EM
Broadus
A E
AE
D000818:Animals; D006801:Humans; D066298:In Vitro Techniques; D008845:Microinjections; D009865:Oocytes / Q000378:metabolism*; D010280:Parathyroid Glands / Q000032:analysis; D010281:Parathyroid Hormone / Q000378:metabolism*; D011061:Poly A / Q000008:administration & dosage; D011233:Precipitin Tests; D011498:Protein Precursors / Q000378:metabolism; D011499:Protein Processing, Post-Translational; D012333:RNA, Messenger / Q000008:administration & dosage; D014982:Xenopus laevis
D010281:Parathyroid Hormone; D011498:Protein Precursors; D012333:RNA, Messenger; D011061:Poly A; C003219:proparathormone; C019056:preproparathormone