Ancient Cytokines,the Role of Astakines as Hematopoietic Growth Factors |
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Authors: | Xionghui Lin Marian Novotny Kenneth S?derh?ll Irene S?derh?ll |
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Institution: | From the ‡Department of Comparative Physiology, Uppsala University, Norbyvägen 18A, 752 36 Uppsala, Sweden and ;the §Department of Cell Biology, Faculty of Sciences, Charles University in Prague, Vinicna 7, Praha 12843, Czech Republic |
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Abstract: | Hematopoiesis is the process by which hemocytes mature and subsequently enter the circulation. Vertebrate prokineticins (PKs) are known to take part in this process, as are the invertebrate prokineticin domain proteins, astakines. In Pacifastacus leniusculus, astakine 1 is essential for the release of new hemocytes into the open circulatory system of these animals. In addition to astakine 1, we have now cloned a homologue of astakine 1 with an insert of 13 amino acids, named as astakine 2. Both crustacean astakines lack the N-terminal AVIT motif, which is present in vertebrate PKs, and hence receptor binding differs from that of vertebrate PKs. We have found astakine-like sequences in 19 different invertebrate species, and the sequences show that some motifs are conserved among invertebrate groups. Previously we showed that astakine 1 is directly involved in hematopoiesis, and now we show that astakine 1 and astakine 2 have different roles in hemocyte lineage differentiation. Astakine 1 can stimulate proliferation of hematopoietic tissue (Hpt) cells (precursor of hemocytes) as well as specifically induce differentiation of Hpt cells along the semigranular cell lineage, whereas astakine 2 plays a role in granular cell differentiation. Moreover, we discuss the impact of the putative structures of different astakines in comparison with the vertebrate prokineticins. |
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Keywords: | Cytokine Differentiation Growth Factors Hematopoiesis Immunology Astakine Hemocyte Invertebrate Prokineticin Proliferation |
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