Relationship between platelet imidazoline receptor-binding peptides and candidate imidazoline-1 receptor, IRAS.
A candidate human imidazoline-1 receptor, designated imidazoline receptor antisera-selected (IRAS) protein, was cloned based on immunoreactivity with antiserum against a purified imidazoline receptor binding peptide (IRBP antiserum). Human IRAS is 167 kD in size, different from 33- to 85-kD IRBP bands previously linked to the human platelet I(1) receptor. To explore the possible relationship between IRAS and these smaller proteins, seven different epitope-specific antisera against IRAS were raised in rabbits for comparison with IRBP antiserum. Focus was on antiserum(227-241), corresponding to amino acids No. 227 to 241 in IRAS, because this antiserum was found uniquely able to immunoprecipitate non-denatured 85-kD and 170-kD forms of IRAS from a human megakaryoblastoma cell line (MEG01), a model of platelet-producing cells. Human platelets lacked the 170-kD form of IRAS, but 33-kD and 85-kD bands were detectable and seemed to be possible fragments of full-length IRAS. The intensity of the 85-kD band detected by antiserum(227-241) was significantly correlated (r = 0.62, P = 0.04) with the intensity of the 33-kD band across 11 human platelet samples. A positive correlation between the intensities of the 33-kD and 85-kD bands is consistent with both being fragments of IRAS.
Zhu
He
H
Department of Psychiatry, University of Mississippi Medical Center, Jackson, Mississippi 39216, USA.
Hayes
Jonathan
J
Chen
Michael
M
Baldwin
James
J
Piletz
John E
JE
D000328:Adult; D000595:Amino Acid Sequence; D000818:Animals; D001792:Blood Platelets / Q000378:metabolism*; D002352:Carrier Proteins / Q000737:chemistry / Q000378:metabolism*; D045744:Cell Line, Tumor; D000939:Epitopes; D005260:Female; D006801:Humans; D054755:Imidazoline Receptors; D015151:Immunoblotting; D047908:Intracellular Signaling Peptides and Proteins; D008297:Male; D008875:Middle Aged; D008969:Molecular Sequence Data; D010455:Peptides / Q000378:metabolism*; D011817:Rabbits; D011955:Receptors, Drug / Q000378:metabolism*; D013223:Statistics as Topic
D002352:Carrier Proteins; D000939:Epitopes; D054755:Imidazoline Receptors; D047908:Intracellular Signaling Peptides and Proteins; C458505:NISCH protein, human; D010455:Peptides; D011955:Receptors, Drug