Heterogeneity of Platelet Fc-receptor-dependent Response to Activating Monoclonal Antibodies

T lineage-specific activation antigen 1 (TLiSA1) antigen was initially described as a T lineage-specific activation antigen involved in the differentiation of human cytotoxic T cells. Subsequently, the antigen was identified on platelets and was shown to be involved in platelet activation, hence it was renamed platelet and T cell antigen 1 (PTA1), although identity between the two antigens was not established. In the present study we have cloned the cDNA encoding TLiSA1 from Jurkat cells and show it to be a novel member of the immunoglobulin superfamily with the unusual structure of two V domains only. Identity between TLiSA1 and platelet PTA1 is established by immunological criteria, by internal peptide sequences obtained from the purified platelet glycoprotein and by sequencing the platelet transcript after reverse transcriptase-polymerase chain reaction. In Jurkat cells, TLiSA1/PTA1 mRNA and surface protein expression is greatly stimulated by treatment of the cells with phorbol ester, but the T cell proliferative signal of phorbol ester and ionophore combined greatly reduces or abrogates this response, and this suppressive effect of the ionophore is not reversed by incorporating FK506 to inhibit calcineurin. Together with the known signaling role of PTA1, these data substantiate the notion that this molecule is implicated in T cell differentiation, perhaps by engagement of an adhesive ligand.

Section: Resultsmentioning

confidence: 99%

Section: Fig 3 Alignments Of the Two V Domains Of Tlisa1 With Reprementioning

confidence: 99%

Section: Fig 3 Alignments Of the Two V Domains Of Tlisa1 With Reprementioning

confidence: 99%

See 1 more Smart Citation

TLiSA1 (PTA1) Activation Antigen Implicated in T Cell Differentiation and Platelet Activation Is a Member of the Immunoglobulin Superfamily Exhibiting Distinctive Regulation of Expression

Sherrington¹,

Scott²,

Jin³

et al. 1997

“…The B6H12 antibody to IAP aggregated platelets only from the responder group suggesting that, as with other activating antibodies, Fc receptor engagement is required for this response (data not shown). Also in common with other platelet-activating antibodies (19,43,34), B6H12 antibody-induced platelet aggregation was preceded by a prolonged lag phase (Fig. 3B), the length of which correlated with the concentration of antibody used (data not shown).…”

Section: Effects Of Cell Binding Peptides From Other Domains Of Thrommentioning

confidence: 97%

Stimulation of Platelet Activation and Aggregation by a Carboxyl-terminal Peptide from Thrombospondin Binding to the Integrin-associated Protein Receptor

Dorahy

Thorne

Fecondo

et al. 1997

Thrombospondin, a major secretory product of the ␣-granules of activated platelets, is a large trimeric glycoprotein that plays an important role in platelet aggregation. On resting platelets, thrombospondin binds to a single receptor in a cation-independent manner, but upon platelet activation it binds at least two further, distinct receptors that are both dependent upon divalent cations. Each of these receptors on the platelet surface binds to different regions of the thrombospondin molecule, and such binding may be responsible for the multifunctional role of thrombospondin in aggregation. We show here that a peptide from the carboxyl terminus of thrombospondin, RFYVVMWK, directly and specifically induces the activation and aggregation of washed human platelets from different donors at concentrations of 5-25 M. At lower concentrations the peptide synergizes with suboptimal concentrations of ADP to induce aggregation. Peptide affinity chromatography and immunoprecipitation with a monoclonal antibody were used to identify the receptor for the carboxyl-terminal peptide as the integrin-associated protein. The integrinassociated protein remained bound to the RFYVVMWKcontaining peptide column when washed with a scrambled peptide in the presence of 5 mM EDTA, indicating a divalent cation-independent association. It is suggested that integrin-associated protein is the primary receptor for thrombospondin on the surface of resting platelets and is implicated in potentiating the platelet aggregation response.

“…41 and 42). A study using chemical cross-linking demonstrated that CD36 is spatially associated with the ␣ IIb ␤ 3 integrin on the surface of platelets (43), and although the functional consequence of this association is not known, it has been shown that platelet activation achieved by the addition of anti-CD36 antibodies involves signaling through this integrin (44,45). It is not known whether CD36 directly associates with integrins on other cell types (12), but there are several lines of evidence to suggest that certain functions ascribed to CD36 directly involve or implicate involvement of integrins.…”

mentioning

confidence: 99%

The Integrins α3β1 and α6β1 Physically and Functionally Associate with CD36 in Human Melanoma Cells

Thorne¹,

Marshall²,

Shafren³

et al. 2000

Lateral association between different transmembrane glycoproteins can serve to modulate integrin function. Here we characterize a physical association between the integrins ␣ 3 ␤ 1 and ␣ 6 ␤ 1 and CD36 on the surface of melanoma cells and show that ectopic expression of CD36 by CD36-negative MV3 melanoma cells increases their haptotactic migration on extracellular matrix components. The association was demonstrated by co-immunoprecipitation, reimmunoprecipitation, and immunoblotting of surface-labeled cells lysed in Brij 96 detergent. Confocal microscopy illustrated the co-association of ␣ 3 and CD36 in cell membrane projections and ruffles. A requirement for the extracellular domain of CD36 in this association was shown by co-immunoprecipitation experiments using surface-labeled MV3 melanoma or COS-7 cells that had been transiently transfected with chimeric constructs between CD36 and intercellular adhesion molecule 1 (ICAM-1) or with a truncation mutant of CD36. CD36 is known to engage in signal transduction and to localize to membrane microdomains or rafts in several cell types. Toward a mechanistic explanation for the functional effects of CD36 expression, we demonstrate that in fractionated Triton X-100 lysates of the MV3 cells stably transfected with CD36, CD36 was greatly enriched with the detergent-insoluble fractions that represent plasma membrane rafts. Significantly, when these fractionated lysates were reprobed for endogenous ␤ 1 integrin, it was found that a 4-fold increase in the proportion of the mature protein was contained within the detergent-insoluble fractions when extracted from the CD36-transfected cells compared with MV3 cells transfected with vector only. These results suggest that in melanoma cells CD36 expression may induce the sequestration of certain integrins into membrane microdomains and promote cell migration.Integrins comprise a large family of ␣␤ heterodimeric transmembrane proteins that function as key receptors for cellular attachment to the extracellular matrix and to cellular ligands (1). Integrin function extends beyond cell adhesion per se, and integrin-mediated signaling influences a range of biological processes including cellular division and migration, differentiation, and apoptosis (reviewed in Refs.