Tryptase beta-2(Tpsb2), also known as Mast cell protease 6(mMCP-6), belongs to the peptidase S1 family and Tryptase subfamily. Tryptase is the major neutral protease present in mast cells and is secreted upon the coupled activation-degranulation response of this cell type. It plays a role in innate immunity. Tpsb2 can be detected primarily in skin during embryogenesis. Tpsb2 can not be detected at early embryonic stages but is abundantly expressed in later stages with a peak at E17.5-E18.5. Tryptase is a homotetramer. The active tetramer is converted to inactive monomers at neutral and acidic pH in the absence of heparin. Low concentrations of inactive monomers become active monomers at pH 6.0 in the presence of heparin. When the concentration of active monomers is higher, they convert to active monomers and then to active tetramers. These monomers are active and functionally distinct from the tetrameric enzyme. In contrast to the hidden active sites in the tetrameric form, the active site of the monomeric form is accessible for macromolecular proteins and inhibitors eg: fibrinogen which is a substrate for the monomeric but not for the tetrameric form. The monomeric form forms a complex with SERPINB6.
Macrophage colony-stimulating factor 1（M-csf）is a single-pass type I membrane protein . It is a hematopoietic growth factor that is involved in the proliferation, differentiation, and survival of monocytes, macrophages, and bone marrow progenitor cells. M-CSF affects macrophages and monocytes in several ways, including stimulating increased phagocytic and chemotactic activity, and increased tumour cell cytotoxicity. The role of M-CSF is not only restricted to the monocyte/macrophage cell lineage. By interacting with its membrane receptor, M-CSF also modulates the proliferation of earlier hematopoietic progenitors and influence numerous physiological processes involved in immunology, metabolism, fertility and pregnancy.
M-CSFR encoded by the proto-oncogene c-fms is the receptor for colony stimulating factor 1 (CSF1R) , a cytokine involved in the proliferation , differentiation , and activation of macrophages. This cell surface glycoprotein is consisted by an extracellular ligand-binding domain , a single membrane-spanning segment , and an intracellular tyrosine kinase domain. Binding of CSF1 activates the receptor kinase , leading to "autophosphorylation" of receptor subunits and the concomitant phosphorylation of a series of cellular proteins on tyrosine residues. CSF1R is a tyrosine kinase receptor that is absolutely required for macrophage differentiation and thus occupies a central role in hematopoiesis. CSF1 and its receptor (CSF1R , product of c-fms proto-oncogene) were initially implicated as essential for normal monocyte development as well as for trophoblastic implantation. This apparent role for CSF1/CSF1R in normal mammary gland development is very intriguing because this receptor/ligand pair has also been found to be important in the biology of breast cancer in which abnormal expression of CSF1 and its receptor correlates with tumor cell invasiveness and adverse clinical prognosis. Tumor cell expression of CSF1R is under the control of several steroid hormones (glucocorticoids and progestins) and the binding of several bHLH transcription factors , while tumor cell expression of CSF-1 appears to be regulated by other hormones , some of which are involved in normal lactogenic differentiation. However , studies have demonstrated that CSF1 and CSF1R have additional roles in mammary gland development during pregnancy and lactation. The role of CSF1 and CSF1R in normal and neoplastic mammary development that may elucidate potential relationships of growth factor-induced biological changes in the breast during pregnancy and tumor progression.
MD-1 and MD-2 are secretory glycoproteins that exist on the cell surface in complexes with transmembrane proteins. MD-1 is anchored by radioprotective 105 (RP105) which is a molecule containing leucine-rich repeats and is expressed on B cells, dentritic cells and macrophages, while MD-2 is associated with TLR4. MD-1 is required for efficient RP105 cell surface expression and function. It is indicated that the RP105/MD1 complex, in conjunction with TLR4, mediates the innate immune response to LPS in B cells, and also plays a role in protecting against apoptosis, B-cell proliferation, etc. Mouse MD-1 cDNA encodes a 162 amino acid precursor protein with a putative 19 aa signal peptide and two potential N-linked glycosylation sites. It shares 40% and 66% amino acid sequence identity with chicken and human MD-1 respectively. MD-1 is mainly expressed in spleen, and also detectable in liver, brain, thymus, and kidney.
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