The dual structural roles of the membrane distal region of the α-integrin cytoplasmic tail during integrin inside-out activation.
Studies on the mechanism of integrin inside-out activation have been focused on the role of β-integrin cytoplasmic tails, which are relatively conserved and bear binding sites for the intracellular activators including talin and kindlin. Cytoplasmic tails for α-integrins share a conserved GFFKR motif at the membrane-proximal region and this forms a specific interface with the β-integrin membrane-proximal region to keep the integrin inactive. The α-integrin membrane-distal regions, after the GFFKR motif, are diverse both in length and sequence and their roles in integrin activation have not been well-defined. In this study, we report that the α-integrin cytoplasmic membrane-distal region contributes to maintaining integrin in the resting state and to integrin inside-out activation. Complete deletion of the α-integrin membrane-distal region diminished talin- and kindlin-mediated integrin ligand binding and conformational change. A proper length and suitable amino acids in α-integrin membrane-distal region was found to be important for integrin inside-out activation. Our data establish an essential role for the α-integrin cytoplasmic membrane-distal region in integrin activation and provide new insights into how talin and kindlin induce the high-affinity integrin conformation that is required for fully functional integrins.
Blood Research Institute, BloodCenter of Wisconsin, Milwaukee, WI 53226, USA.
Jiafu
J
Liu
Blood Research Institute, BloodCenter of Wisconsin, Milwaukee, WI 53226, USA College of Marine Science and Engineering, Qingdao Agricultural University, Qingdao 266109, China.
Zhengli
Z
Wang
Blood Research Institute, BloodCenter of Wisconsin, Milwaukee, WI 53226, USA Department of Biochemistry, Medical College of Wisconsin, Milwaukee, WI 53226, USA.
Aye Myat Myat
AM
Thinn
Blood Research Institute, BloodCenter of Wisconsin, Milwaukee, WI 53226, USA Department of Biochemistry, Medical College of Wisconsin, Milwaukee, WI 53226, USA.
Yan-Qing
YQ
Ma
Blood Research Institute, BloodCenter of Wisconsin, Milwaukee, WI 53226, USA Department of Biochemistry, Medical College of Wisconsin, Milwaukee, WI 53226, USA Jieqing.Zhu@bcw.edu.
Jieqing
J
Zhu
D000818:Animals; D002352:Carrier Proteins / Q000378:metabolism; D003593:Cytoplasm / Q000737:chemistry*; D006801:Humans; D039001:Integrin alpha Chains / Q000737:chemistry* / Q000378:metabolism*; D039661:Integrin beta3 / Q000737:chemistry / Q000378:metabolism; D020014:K562 Cells; D051379:Mice; D050505:Mutant Proteins / Q000378:metabolism; D009154:Mutation / Q000235:genetics; D011485:Protein Binding / Q000187:drug effects; D055503:Protein Multimerization / Q000187:drug effects; D017434:Protein Structure, Tertiary; D017384:Sequence Deletion; D013329:Structure-Activity Relationship; D016608:Talin / Q000378:metabolism; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
D002352:Carrier Proteins; D039001:Integrin alpha Chains; D039661:Integrin beta3; D050505:Mutant Proteins; D016608:Talin; D013755:Tetradecanoylphorbol Acetate
Inside‐out activation; Integrin cytoplasmic domain; Kindlin; Leukocyte; Platelet; Talin