Vol. 173, No. 3, 1990 December 31, 1990 BIOCHEMICAL AND BIOPHYSICAL RESEARCH COMMUNICATIONS Pages 1161-1168 GRANULINS, A NOVEL CLASS OF PEPTIDE FROM LEUKOCYTES Andrew Bateman*, Daniel Belcourt*, Hugh Bennett*, Claude Lazure**, and Samuel Solomon* *Endocrine Laboratory, Royal Victoria Hospital/McGill University, Departments of Medicine, Obstetrics, and Gynecology, Montreal, Quebec, H3A 1A1, Canada **Institut de recherches cliniques de Montr6al, Montreal, Quebec, Canada Received November i, 1990 SUMMARY. We report the isolation and characterization of a novel class of leukocyte peptides with possible cytokine-like activities which we call granulins. They are cystine-rich with molecular weights of approximately 6Kda, except for granulin D, which appears to be a dimer. We present the sequence of one member of this family, a 56 residue peptide, granulin A, and amino-terminal sequences for three other granulins from human peripheral leukocytes. A fifth related peptide was isolated and partially sequenced from rat bone marrow, suggesting that at least some of the granulin in peripheral leukocytes is preformed in the marrow. Rat granulin, and human granulin A, are closely related, showing that the granulin structures are highly conserved between species. ® 1990 Academic Press, Inc. It has recently become clear that leukocytes are peptiderglc cells. Neutrophil granules contain large amounts of basic, cystine-rich peptides of 29 to 34 amino acids, that have been variously called defensins (1), corticostatins (2), myeloid-related sequences (3), and cryptidins (4). Some of these peptides are antimicrobial agents at micromolar concentrations (5), and it was initially thought that their only biological activity was in non-oxidative, non-enzymatic, destruction of phagocytosed microorganisms. More recently, however, we have shown that corticostatins have potential regulatory functions, including the ability to inhibit the action of the hormone adrenocorticotropin on glucocorticoid secretion (2,6,7) and to stimulate nifedipine-sensitive L-type Ca 2+ channels in villus enterocytes (8). It has also been reported that a human defensin is a monocyte chemotactic agent (9). Other granulocyte-associated peptides have also been shown to have regulatory activities. For example, hemoregulatory peptide 1 is a granulocyte-associated thiol containing pentapeptide, with potent inhibitory actions on myelopoiesis (10). Several groups have reported the existence of immunomodulatory or cytokine-like activities associated with neutrophll extracts or supernatants (11,12,13,14). These activities include mast cell degranulation, chemotaxis, and the inhibition of myelopoetic-colony formation. Despite these reports, and the evidence for regulatory actions associated with known granulocyte peptides, few systematic attempts to Abbreviations. TFA, trifluoroacetic acid: HFBA, heptafluorobutyric acid; rp-HPLC reverses phase high performance liquid chromatography; PTH, phenylthiohydantoin. 1161 0006-291X/90 $1.50 Copyright © 1990 by Academic Press. lnc. All rights of reproduction in any form reserved.