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Medical SciencesSer-752 -> Pro mutation in the cytoplasmic domain of integrin .83 subunit and defective activation of platelet integrin aIlbP3 (glycoprotein lib-Illa) in a variant of Glanzmann thrombasthenia (molcular genetlcs/flbnnogen receptor/Arg-Gly-Asp/poyerase chan reacdon) YI-PING CHEN*, ISABELLE DJAFFAR*, DOMINIQUE PIDARDt, BEAT (8,9), as well as for aLI32 (10). At least in the case of amb43 activation, modulation of affinity for its ligands is coordinated with conformational changes of the integrin (7,11). What remains obscure is the exact link between intracellular signals and aIIbP3 conformation modulation.Glanzmann thrombasthenia is a hereditary bleeding disorder characterized by the absence of platelet aggregation due to either an absence or a functional alteration of the integrin aII03 (12). In several cases, the genetic basis for the quantitative defect was found to be associated with alterations within the genes of ajib,83 subunits-i.e., either aib (glycoprotein lIb) (13,14) or 83 (glycoprotein IIa) (14, 15). In addition, the qualitative defects in aIlbm3 found in variants of Glanzmann thrombasthenia have also become the focus of investigations, and two mutations in Glanzmann variants that disrupted ligand binding sites of (3 have been characterized (16-18). Here we report a variant of Glanzmann thrombasthenia whose biochemical and genetic analyses are consistent with the idea that the functional defect is due to replacement of serine by proline in position 752 in the cytoplasmic domain of P3 and that this mutation impairs the coupling between cellular activation and up-regulation of arnb,83 affinity for fibrinogen. To our knowledge this is the first point mutation reported affecting integrin activation. METHODSPatient's Case. Patient P.'s case of variant Glanzmann thrombasthenia has been previously reported (19). Briefly, patient P. exhibited a life-long bleeding tendency with failure of platelets to aggregate and to bind fibrinogen in response to agonists such as ADP, collagen, or thrombin. The patient's platelets could support clot retraction. The presence of alb/3 in the patient's platelets was established by immunocytochemistry.Protein Analysis and Monoclonal Antibody Binding. Blood was collected in the presence of 5 mM EDTA, and platelets were prepared by conventional methods (20). Platelet proteins were solubilized in 2% NaDodSO4 and two-dimensional nonreduced/reduced NaDodSO4/PAGE was performed as described (21). Total platelet proteins (200 ,ug) were solubilized in 2% NaDodSO4 and separated in a first dimension in a 6% polyacrylamide tube gel. Disulfide bonds were reduced by soaking the gel in 10%6 (vol/vol) 2-mercaptoethanol, and the proteins were then separated again in a perpendicular direction in a 7-12% polyacrylamide slab gel. Proteins were detected by staining with Coomassie blue-R.The monoclonal antibody AP-2, which is specific for glycoprotein Ilb-IIla (22), the a11b13 integrin (a generous gift Abbreviations: RGDS, Arg-Gly-Asp-Ser; nt, nucleotide(s). lTo whom reprint requests...

The present paper is devoted to the study of short peptides derived from milk proteins with physiological activities. Some of them behaved as opioids, enzyme inhibitors that convert angiotensin I, peptides that enhance calcium absorption, antiaggregating and antithrombotic peptides, and immunomodulating peptides. Some possessed several physiological properties, such as the C-terminal part of bovine alpha s1-casein. A strategic zone, containing immunostimulating and opioid peptides, could be located in cow and human beta-caseins. Few of these peptides or precursor peptides have so far been characterized in vivo in blood or brain after ingestion of milk. If, in the future, some of the active peptides cannot be characterized in vivo, they can all nevertheless be synthesized and used either as food additives or in pharmacology.

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