J. Biol. Chem., Vol. 265, Issue 1, 58-62, Jan, 1990
Characterization of fully active biotinylated parathyroid hormone analogs. Application to fluorescence-activated cell sorting of parathyroid hormone receptor bearing cells
AB Abou-Samra, M Freeman, H Juppner, S Uneno and GV Segre
Department of Medicine, Massachusetts General Hospital, Harvard Medical School, Boston 02114.
[Nle8,18,Tyr34]bPTH-(1-34)amide (NlePTH) was biotinylated using
sulfosuccinimidyl 6-(biotinamido)hexanoate, in dimethyl sulfoxide, and the
multiple resulting peptides peaks were separated by reverse-phase high
performance liquid chromatography. Their biological activities were
compared with those of NlePTH, the parent compound, in radioreceptor and
cAMP accumulation bioassays using rat osteosarcoma 17/2.8 cells; the
earliest two eluting products, bioPTH 1 and 2, were equipotent, a third,
bioPTH 3, was only 10% as potent, and the remaining, later eluting
derivatives all were less than 0.1% as active. Competitive avidin binding
assays using [3H]biotin suggested that bioPTH 1 and 2 had a single biotin
congener per molecule, while bioPTH 3 contained two biotin residues. Upon
Edman degradation, bioPTH 1 contained biotin on the lysine at position 13
of NlePTH; bioPTH 2's biotin was on the lysine at position 26 (or 27) and
bioPTH 3 had biotins on lysines at both positions 13 and 26 (or 27). Avidin
tagged with 125I, peroxidase, or fluorescein isothiocyanate was detected on
bone-derived cells which had been incubated initially with bioPTH 2 (1, 10,
and 100 nM) for 4 h, but not when NlePTH (1 microM) was added with bioPTH
2. A fluorescence-activated cell sorter detected a symmetrical shift in
fluorescence of bone-derived cells incubated with 10 nM of bioPTH 2 and 10
micrograms/ml fluorescein isothiocyanate-avidin. Addition of a 30-fold
molar excess of NlePTH, or omission of bioPTH 2, completely reversed this
fluorescence shift, and no shift in fluorescence was seen with cells
lacking PTH receptors. This fully active, high affinity biotinylated
PTH-derivative should prove useful in the study of PTH receptor-bearing
cells.