IGFBP-1 protease activity and IGFBP-1 fragments in a patient with multiple myeloma.
OBJECTIVE
Cleavage of IGFBPs by proteases results in IGFBP fragments that have altered IGF-binding affinity, and IGF-independent roles. We have previously purified a specific IGFBP-1 protease activity from the urine of an individual with multiple myeloma and dermatitis. The aim of this study was to determine whether IGFBP-1 protease activity and/or IGFBP-1 fragments were present in the circulation of this patient.


METHODS
The size of immunoreactive IGFBP-1 in serum samples was determined after Superose 12 chromatography. Intact IGFBP-1 and IGFBP-1 fragments were characterized in four RIAs and after SDS-PAGE.


RESULTS
Specific proteolysis of IGFBP-1 generated an N-terminal fragment (IGFBP-1(1-130)) with a predicted molecular mass of 13kDa but an apparent mass of 21kDa on SDS-PAGE. A C-terminal fragment (IGFBP-1(131-234)) produced in vitro migrated at 11.4kDa, close to its predicted size. However a C-terminal fragment of cleaved IGFBP-1 (IGFBP-1(142-234)) migrated at 14kDa on SDS-PAGE. Serum from the patient inhibited IGFBP-1 protease activity. Immunoreactive IGFBP-1 in patient serum was present at molecular masses consistent with IGFBP-1 fragments, in addition to intact IGFBP-1.


CONCLUSIONS
Specific cleavage of IGFBP-1 occurs at the tissue level and not in the circulation in a patient with multiple myeloma and dermatitis. The fragments that are generated may have endocrine roles.
Brandt
Katrin
K
Department of Molecular Medicine and Surgery, Karolinska Institutet, L1:01 Karolinska University Hospital Solna, SE-171 76 Stockholm, Sweden.
Wang
Jing
J
Lundell
Kerstin
K
Ståhlberg
Marie
M
Horn
Henrik von
Hv
Ehrenborg
Ewa
E
Hall
Kerstin
K
Jörnvall
Hans
H
Lewitt
Moira
M
D000368:Aged; D023181:Antimicrobial Cationic Peptides / Q000378:metabolism; D019921:Biotinylation; D001798:Blood Proteins / Q000378:metabolism; D002352:Carrier Proteins / Q000378:metabolism; D002845:Chromatography / Q000379:methods; D003872:Dermatitis / Q000097:blood* / Q000378:metabolism*; D005260:Female; D006801:Humans; D018970:Insulin-Like Growth Factor Binding Protein 1 / Q000097:blood* / Q000378:metabolism*; D007334:Insulin-Like Growth Factor I / Q000096:biosynthesis*; D009101:Multiple Myeloma / Q000097:blood* / Q000378:metabolism*; D020033:Protein Isoforms; D011863:Radioimmunoassay / Q000379:methods; D011994:Recombinant Proteins / Q000737:chemistry; D012685:Sepharose / Q000737:chemistry
C062991:AZU1 protein, human; D023181:Antimicrobial Cationic Peptides; D001798:Blood Proteins; D002352:Carrier Proteins; D018970:Insulin-Like Growth Factor Binding Protein 1; D020033:Protein Isoforms; D011994:Recombinant Proteins; D007334:Insulin-Like Growth Factor I; D012685:Sepharose; C049225:Superose 12