title: Evidence that muscle cells do not express the histidine-rich glycoprotein associated with AMP deaminase but can internalise the plasma protein.
abstract: Histidine-rich glycoprotein (HRG) is synthesized by liver and is present at relatively high concentration in the plasma of vertebrates. We have previously described the association of a HRG-like molecule to purified rabbit skeletal muscle AMP deaminase (AMPD). We also provided the first evidence for the presence of a HRG-like protein in human skeletal muscle where a positive correlation between HRG content and total determined AMPD activity has been shown. In the present paper we investigate the origin of skeletal muscle HRG. The screening of a human skeletal muscle cDNA expression library using an anti-HRG antibody failed to reveal any positive clone. The RT-PCR analysis, performed on human skeletal muscle RNA as well as on RNA from the rhabdomyosarcoma (RD) cell line, failed to show any mRNA specific for the plasma HRG or for the putative muscle variant. When the RD cells were incubated with human plasma HRG, a time-dependent increase of the HRG immunoreactivity was detected both at the plasma membrane level and intracellularly. The internalisation of HRG was inhibited by the addition of heparin. The above data strongly suggest that skeletal muscle cells do not synthesize the muscle variant of HRG but instead can actively internalise it from plasma.
authors.affiliation: Dipartimento di Scienze dell’Uomo edell’Ambiente, Chimica e Biochimica Medica, University of Pisa. araggi@med.unipi.it
authors.forename: A R M
authors.initials: AR
authors.lastname: Sabbatini
authors.forename: L
authors.initials: L
authors.lastname: Mattii
authors.forename: B
authors.initials: B
authors.lastname: Battolla
authors.forename: E
authors.initials: E
authors.lastname: Polizzi
authors.forename: D
authors.initials: D
authors.lastname: Martini
authors.forename: M
authors.initials: M
authors.lastname: Ranieri-Raggi
authors.forename: A J G
authors.initials: AJ
authors.lastname: Moir
authors.forename: A
authors.initials: A
authors.lastname: Raggi
mesh_terms: D000659:AMP Deaminase / Q000378:metabolism*; D001798:Blood Proteins / Q000235:genetics / Q000378:metabolism*; D045744:Cell Line, Tumor; D004591:Electrophoresis, Polyacrylamide Gel; D004705:Endocytosis / Q000502:physiology; D014644:Genetic Variation; D006801:Humans; D018482:Muscle, Skeletal / Q000201:enzymology / Q000378:metabolism*; D011485:Protein Binding; D011506:Proteins / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012208:Rhabdomyosarcoma / Q000473:pathology; D000099053:Histidine-Rich Glycoprotein
chemical_list: D001798:Blood Proteins; D011506:Proteins; D012333:RNA, Messenger; D000099053:Histidine-Rich Glycoprotein; D000659:AMP Deaminase