Megakaryocyte maturation is associated with expression of the CXC chemokine connective tissue‐activating peptide CTAP III

Abstract

Summary. Connective tissue-activating peptide III (CTAP III), a CXC chemokine derived from the chemokine precursor platelet basic protein (PBP) by proteolytic cleavage, has been identified in platelets, activated macrophages, neutrophils and T lymphocytes. CTAP III can support stem cell-derived haematopoiesis yet inhibits the proliferation of committed megakaryocyte (MK) progenitors. This investigation was aimed at characterizing CTAP III expression in human MKs and determining it's role in MK differentiation. We report high expression of CTAP III in mature human bone marrow (BM) MKs and megakaryoblast cell lines following differentiation induction with phorbol ester 12-myristate 13-acetate (PMA). Immunostaining with anti-CTAP III antibodies demonstrated its prominent presence in platelet producing zones in the cytoplasm and intense staining around the periphery of the large BM MKs. In cultures of logarithmically growing megakaryoblast cell lines DAMI, CHRF-288 or MEG01, which contain primarily 2N cells, only 15% of the cells expressed CTAP III. The addition of PMA stimulated high levels of CTAP III after 24 h in more than 75% of the cells, being expressed in both the 2N and large polyploid MKs. Reverse transcription polymerase chain reaction (RT-PCR) revealed upregulation of CTAP III mRNA after only 1 h of exposure to PMA that was sustained for 24 h. In the bone marrow of idiopathic thrombocytopenic pupura (ITP) patients undergoing accelerated MK maturation and thrombopoiesis, 99% of large MKs and 95% of small MKs expressed high levels of CTAP III. While the biological function of this chemokine in MKs is not known, these studies demonstrate that molecular upregulation of CTAP III in MKs is associated with maturation and, as with other chemokines, may be involved in proliferation arrest and cellular interactions with extracellular matrix and platelet production.

Induction and antimicrobial activity of platelet basic protein derivatives in human monocytes

“…Our finding that thrombin, a protein of the coagulation cascade, activates host defense cells to express increased amounts of a CXC chemokine with antimicrobial activity, which is also expressed in large amounts by blood platelets that have main functions in hemostasis, can be viewed as further evidence for the coevolution of the immune and coagulation system. More important, these studies show that noxious stimuli, which result in activation of blood coagulation and thrombin formation [53][54][55][56], as well as microbial components and microorganisms, result in an increased expression of PBP. This rapid reaction, independent of the necessity to mount an adoptive immune response, appears meaningful in view of the proposed role of cationic, antimicrobial peptides including PBP and several other chemokines in innate immunity.…”

Crucial Role for Endoplasmic Reticulum Stress During Megakaryocyte Maturation

“…The same treatment also increased the amount of connective tissue-activating peptide III (CTAP III) messengers that code for chemokine receptor that is induced during maturation in PMA-treated DAMI and CHRF 288-11 cells. 34 CTAP III was increased from 100% in untreated cells to 163±53% and 180±68% for DAMI and 142±25% and 190±25% for MEG-01, in the presence of Tun 1 and 4 µg/mL, respectively ( Figure 3B and 3C).…”

Is There a Relationship Between CXCR4 Gene Expression and Prognosis of Immune Thrombocytopenia in Children?

“…Cytokines and chemokines play an important role in megakaryopoiesis, and exert their regulatory mechanisms in proliferation, differentiation and release of platelets [13]. Chemokines are a family of proinflammatory molecules that can be used as activators of platelet function [14,15]. Several chemokines (CCL5, CCL17, CXCL4 and CXCL8) stored in high levels in platelet alpha granules, are released during platelet * * Fig.…”