title: Calpain cleavage promotes talin binding to the beta 3 integrin cytoplasmic domain.
abstract: Talin links integrin beta cytoplasmic domains to the actin cytoskeleton and is involved in the clustering and activation of these receptors. To understand how talin recognizes integrin beta cytoplasmic domains, we configured surface plasmon resonance methodology to measure the interaction of talin with the beta3 integrin cytoplasmic domain. Here we report that the N-terminal approximately 47-kDa talin head domain (talin-H) has a 6-fold higher binding affinity than intact talin for the beta3 tail. The affinity difference is mainly due to a difference in k(on). Calpain cleavage of intact talin released talin-H and resulted in a 16-fold increase in apparent K(a) and a 100-fold increase in apparent k(on). The increase in talin binding after cleavage was greater than predicted for stoichiometric liberation of free talin-H. This additional increase in binding was due to cooperative binding of talin-H and talin rod domain to the beta3 tail. Talin resembles ERM (ezrin, radixin, moesin) proteins in possessing an N-terminal FERM (band four-point-one, ezrin, radixin, moesin) domain. These data show that the talin FERM domain, like that in the ERM proteins, is masked in the intact molecule. Furthermore, they suggest that talin cleavage by calpain may contribute to the effects of the protease on the clustering and activation of integrins.
authors.affiliation: Department of Vascular Biology, The Scripps Research Institute, La Jolla, California 92037, USA.
authors.forename: B
authors.initials: B
authors.lastname: Yan
authors.forename: D A
authors.initials: DA
authors.lastname: Calderwood
authors.forename: B
authors.initials: B
authors.lastname: Yaspan
authors.forename: M H
authors.initials: MH
authors.lastname: Ginsberg
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D015703:Antigens, CD / Q000378:metabolism; D001710:Biotin / Q000378:metabolism; D001792:Blood Platelets / Q000378:metabolism; D002154:Calpain / Q000378:metabolism*; D003593:Cytoplasm / Q000378:metabolism; D003599:Cytoskeleton / Q000378:metabolism; D018076:DNA, Complementary / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D008401:Gas Chromatography-Mass Spectrometry; D006801:Humans; D039661:Integrin beta3; D016023:Integrins / Q000378:metabolism; D007700:Kinetics; D008969:Molecular Sequence Data; D010980:Platelet Membrane Glycoproteins / Q000378:metabolism; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D051381:Rats; D011994:Recombinant Proteins / Q000378:metabolism; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D020349:Surface Plasmon Resonance; D016608:Talin / Q000378:metabolism*; D013997:Time Factors
chemical_list: D015703:Antigens, CD; D018076:DNA, Complementary; D039661:Integrin beta3; D016023:Integrins; D010980:Platelet Membrane Glycoproteins; D011994:Recombinant Proteins; D016608:Talin; D001710:Biotin; D002154:Calpain