Thrombospondins (TSPs) are a family of secreted

glycoprotein Glycoproteins are proteins which contain oligosaccharide chains covalently attached to amino acid side-chains. The carbohydrate is attached to the protein in a cotranslational or posttranslational modification. This process is known as glyco ...

s with

antiangiogenic An angiogenesis inhibitor is a substance that inhibits the growth of new blood vessels (angiogenesis). Some angiogenesis inhibitors are endogenous and a normal part of the body's control and others are obtained exogenously through pharmaceutical dr ...

functions. Due to their dynamic role within the

extracellular matrix In biology, the extracellular matrix (ECM), also called intercellular matrix, is a three-dimensional network consisting of extracellular macromolecules and minerals, such as collagen, enzymes, glycoproteins and hydroxyapatite that provide s ...

they are considered

matricellular proteins A matricellular protein is a dynamically expressed non-structural protein that is present in the extracellular matrix (ECM). Rather than serving as stable structural elements in the ECM, these proteins are rapidly turned over and have regulatory ro ...

. The first member of the family,

thrombospondin 1 Thrombospondin 1, abbreviated as THBS1, is a protein that in humans is encoded by the ''THBS1'' gene. Thrombospondin 1 is a subunit of a disulfide-linked homotrimeric protein. This protein is an adhesive glycoprotein that mediates cell-to-cell an ...

(THBS1), was discovered in 1971 by Nancy L. Baenziger.

Types

The thrombospondins are a family of multifunctional proteins. The family consists of thrombospondins 1-5 and can be divided into 2 subgroups: A, which contains TSP-1 and TSP-2, and B, which contains TSP-3, TSP-4 and TSP-5 (also designated cartilage oligomeric protein or COMP). TSP-1 and TSP-2 are homotrimers, consisting of three identical subunits, whereas TSP-3, TSP-4 and TSP-5 are homopentamers. TSP-1 and TSP-2 are produced by immature

astrocyte Astrocytes (from Ancient Greek , , "star" + , , "cavity", "cell"), also known collectively as astroglia, are characteristic star-shaped glial cells in the brain and spinal cord. They perform many functions, including biochemical control of e ...

s during brain development, which promotes the development of new

synapse In the nervous system, a synapse is a structure that permits a neuron (or nerve cell) to pass an electrical or chemical signal to another neuron or to the target effector cell. Synapses are essential to the transmission of nervous impulses from ...

Thrombospondin 1

Thrombospondin 1 (TSP-1) is encoded by

THBS1 Thrombospondin 1, abbreviated as THBS1, is a protein that in humans is encoded by the ''THBS1'' gene. Thrombospondin 1 is a subunit of a disulfide-linked homotrimeric protein. This protein is an adhesive glycoprotein that mediates cell-to-cell and ...

. It was first isolated from

platelets Platelets, also called thrombocytes (from Greek θρόμβος, "clot" and κύτος, "cell"), are a component of blood whose function (along with the coagulation factors) is to react to bleeding from blood vessel injury by clumping, thereby ...

that had been stimulated with thrombin, and so was designated 'thrombin-sensitive protein'. Since its first recognition, functions for TSP-1 have been found in multiple biological processes including angiogenesis, apoptosis, activation of

TGF-beta Transforming growth factor beta (TGF-β) is a multifunctional cytokine belonging to the transforming growth factor superfamily that includes three different mammalian isoforms (TGF-β 1 to 3, HGNC symbols TGFB1, TGFB2, TGFB3) and many other ...

and Immune regulation. As such, TSP-1 is designated a multifunctional protein. TSP-1 has multiple receptors, among which CD36,

CD47 CD47 (Cluster of Differentiation 47) also known as integrin associated protein (IAP) is a transmembrane protein that in humans is encoded by the CD47 gene. CD47 belongs to the immunoglobulin superfamily and partners with membrane integrins and ...

and

integrins Integrins are transmembrane receptors that facilitate cell-cell and cell-extracellular matrix (ECM) adhesion. Upon ligand binding, integrins activate signal transduction pathways that mediate cellular signals such as regulation of the cell cycle, ...

are of particular note. TSP-1 is

, inhibiting the proliferation and migration of endothelial cells by interactions with CD36 expressed on their surface of these cells. Inhibitory peptides and fragments of

TSP1 Thrombospondin 1, abbreviated as THBS1, is a protein that in humans is encoded by the ''THBS1'' gene. Thrombospondin 1 is a subunit of a disulfide-linked homotrimeric protein. This protein is an adhesive glycoprotein that mediates cell-to-cell and ...

bind to CD36, leading to the expression of FAS ligand (FasL), which activates its specific, ubiquitous receptor, Fas. This leads to the activation of

caspase Caspases (cysteine-aspartic proteases, cysteine aspartases or cysteine-dependent aspartate-directed proteases) are a family of protease enzymes playing essential roles in programmed cell death. They are named caspases due to their specific cyste ...

s and

apoptosis Apoptosis (from grc, ἀπόπτωσις, apóptōsis, 'falling off') is a form of programmed cell death that occurs in multicellular organisms. Biochemical events lead to characteristic cell changes ( morphology) and death. These changes in ...

of the cell. Since tumors overexpressing TSP-1 typically grow slower, exhibit less angiogenesis, and have fewer metastases, TSP1 is an attractive target for cancer treatment. Because

is extremely large (~120

kDa The dalton or unified atomic mass unit (symbols: Da or u) is a non-SI unit of mass widely used in physics and chemistry. It is defined as of the mass of an unbound neutral atom of carbon-12 in its nuclear and electronic ground state and at re ...

monomer), not very abundant and exerts multiple actions, its clinical usefulness is questionable. However, small-molecules based on a CD36-binding peptide sequence from

are being tested. One analog,

ABT-510 ABT-510 is a molecular therapeutic drug that was the subject of research as a potential treatment for cancer. According to the ''Journal of Clinical Oncology'', ABT-510 is a "subcutaneously (SC) administered nonapeptide thrombospondin analogue."

, exhibits potent proapoptotic activity in cultured cells, while clinically it is very well tolerated with therapeutic benefits reported against several malignancies. In 2005, ABT-510 was evaluated in phase II clinical trials for the treatment of several types of cancer.

Human proteins containing this domain

ADAMTS1; ADAMTS10;

ADAMTS12 A disintegrin and metalloproteinase with thrombospondin motifs 12 is an enzyme that in humans is encoded by the ''ADAMTS12'' gene. This gene encodes a member of the ADAMTS (a disintegrin and metalloproteinase with thrombospondin motifs) protein ...

;

ADAMTS13 ADAMTS13 (''a disintegrin and metalloproteinase with a thrombospondin type 1 motif, member 13'')—also known as ''von Willebrand factor-cleaving protease'' (VWFCP)—is a zinc-containing metalloprotease enzyme that cleaves von Willebrand facto ...

;

ADAMTS14 ADAMTS14 encodes a member of the ADAMTS protein family. Members of the family share several distinct protein modules, including a propeptide region, a metalloproteinase domain, a disintegrin-like domain, and a thrombospondin type 1 (TS) motif. Indi ...

; ADAMTS15; ADAMTS16; ADAMTS17; ADAMTS18; ADAMTS19;

ADAMTS2 A disintegrin and metalloproteinase with thrombospondin motifs 2 (ADAM-TS2) also known as procollagen I N-proteinase (PC I-NP) is an enzyme that in humans is encoded by the ''ADAMTS2'' gene. Gene The ADAMTS2 gene is located on the long (q) ...

;

ADAMTS20 ADAMTS (short for a disintegrin and metalloproteinase with thrombospondin motifs) is a family of multidomain extracellular protease enzymes. 19 members of this family have been identified in humans, the first of which, ADAMTS1, was described in 1997 ...

;

ADAMTS3 A disintegrin and metalloproteinase with thrombospondin motifs 3 is an enzyme that in humans is encoded by the ''ADAMTS3'' gene. The protein encoded by this gene is the major procollagen II N-propeptidase. Structure This gene encodes a membe ...

; ADAMTS4; ADAMTS5;

ADAMTS6 ADAM metallopeptidase with thrombospondin type 1 motif 6 is a protein that in humans is encoded by the ADAMTS6 gene. Function This gene encodes a member of the ADAMTS (a disintegrin and metalloproteinase with thrombospondin motifs) protein f ...

; ADAMTS7; ADAMTS8; ADAMTS9; ADAMTSL1; ADAMTSL2; ADAMTSL3; ADAMTSL4; ADAMTSL5; BAI1;

BAI2 BAI or Bai may refer to: BAI Organizations *BAI Communications, telecommunications infrastructure company * BAI (organization), professional organization for financial services in the United States * Badminton Association of India, India's go ...

; BAI3; C6; C7; C8A; C8B; C9; C9orf8; C9orf94; CFP; CILP; CILP2;

CTGF CTGF, also known as CCN2 or connective tissue growth factor, is a matricellular protein of the CCN family of extracellular matrix-associated heparin-binding proteins (see also CCN intercellular signaling protein). CTGF has important roles in many ...

;

CYR61 Cysteine-rich angiogenic inducer 61 (CYR61) or CCN family member 1 (CCN1), is a matricellular protein that in humans is encoded by the ''CYR61'' gene. CYR61 is a secreted, extracellular matrix (ECM)-associated signaling protein of the CCN family ...

; HMCN1;

LIBC The C standard library or libc is the standard library for the C programming language, as specified in the ISO C standard. ISO/IEC (2018). '' ISO/IEC 9899:2018(E): Programming Languages - C §7'' Starting from the original ANSI C standard, it was ...

; NOV; PAPLN;

RSPO1 R-spondin-1 is a secreted protein that in humans is encoded by the ''Rspo1'' gene, found on chromosome 1. In humans, it interacts with WNT4 in the process of female sex development. Loss of function can cause female to male sex reversal. Furthe ...

; RSPO3;

SEMA5A Semaphorin-5A is a protein that in humans is encoded by the ''SEMA5A'' gene. Members of the semaphorin protein family, such as SEMA5A, are involved in axonal guidance during neural development. Semaphorin 5A also plays a role in autism, reduc ...

; SEMA5B; SPON1; SPON2;

SSPO SCO-spondin is a protein that in humans is encoded by the ''SSPO'' gene. SCO-spondin is secreted by the subcommissural organ, and contributes to commissural axon growth and the formation of Reissner's fiber Reissner's fiber ''(named after E ...

;

THBS2 Thrombospondin-2 is a protein that in humans is encoded by the ''THBS2'' gene. The protein encoded by this gene belongs to the thrombospondin family. It is a disulfide-linked homotrimeric glycoprotein that mediates cell-to-cell and cell-to-matrix ...

; THSD1; THSD3; THSD7A; THSD7B; UNC5A; UNC5B; UNC5C; UNC5D;

WISP1 WNT1-inducible-signaling pathway protein 1 (WISP-1), also known as CCN4, is a matricellular protein that in humans is encoded by the ''WISP1'' gene. Structure WISP-1 is highly homologous to CYR61 (CCN1) and CTGF (CCN2), and is a member of t ...

;

WISP2 WNT1-inducible-signaling pathway protein 2, or WISP-2 (also named CCN5) is a matricellular protein that in humans is encoded by the ''WISP2'' gene. Function The CCN family of proteins regulates diverse cellular functions, including cell adhesi ...

;

WISP3 WNT1-inducible-signaling pathway protein 3 (WISP3, also named CCN6) is a matricellular protein that in humans is encoded by the ''WISP3'' gene. Structure It is a member of the CCN family ( CCN intercellular signaling protein) of secreted, extra ...

;

References

External links

* * , , , , {{Gene, COMP (also known as "THBS5") Protein domains