Defining extracellular integrin alpha-chain sites that affect cell adhesion and adhesion strengthening without altering soluble ligand binding.
It was previously shown that mutations of integrin alpha4 chain sites, within putative EF-hand-type divalent cation-binding domains, each caused a marked reduction in alpha4beta1-dependent cell adhesion. Some reports have suggested that alpha-chain "EF-hand" sites may interact directly with ligands. However, we show here that mutations of three different alpha4 "EF-hand" sites each had no effect on binding of soluble monovalent or bivalent vascular cell adhesion molecule 1 whether measured indirectly or directly. Furthermore, these mutations had minimal effect on alpha4beta1-dependent cell tethering to vascular cell adhesion molecule 1 under shear. However, EF-hand mutants did show severe impairments in cellular resistance to detachment under shear flow. Thus, mutation of integrin alpha4 "EF-hand-like" sites may impair 1) static cell adhesion and 2) adhesion strengthening under shear flow by a mechanism that does not involve alterations of initial ligand binding.
Pujades
C
C
Division of Tumor Virology, Dana-Farber Cancer Institute, Harvard Medical School, Boston, Massachusetts 02115, USA.
Alon
R
R
Yauch
R L
RL
Masumoto
A
A
Burkly
L C
LC
Chen
C
C
Springer
T A
TA
Lobb
R R
RR
Hemler
M E
ME
D000595:Amino Acid Sequence; D019943:Amino Acid Substitution / Q000235:genetics; D015703:Antigens, CD / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D001665:Binding Sites; D002413:Cations, Divalent / Q000378:metabolism / Q000494:pharmacology; D002448:Cell Adhesion / Q000187:drug effects; D020832:EF Hand Motifs; D005353:Fibronectins / Q000737:chemistry / Q000378:metabolism; D006801:Humans; D007074:Immunoglobulin G / Q000378:metabolism; D039441:Integrin alpha4; D039041:Integrin alpha4beta1; D016023:Integrins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D020014:K562 Cells; D008024:Ligands; D008345:Manganese / Q000378:metabolism / Q000494:pharmacology; D009154:Mutation / Q000235:genetics; D010446:Peptide Fragments / Q000737:chemistry / Q000378:metabolism; D011485:Protein Binding / Q000187:drug effects; D016201:Receptors, Lymphocyte Homing / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000378:metabolism; D012995:Solubility; D014162:Transfection; D019010:Vascular Cell Adhesion Molecule-1 / Q000737:chemistry / Q000378:metabolism
D015703:Antigens, CD; D002413:Cations, Divalent; D005353:Fibronectins; D007074:Immunoglobulin G; D039041:Integrin alpha4beta1; D016023:Integrins; D008024:Ligands; D010446:Peptide Fragments; D016201:Receptors, Lymphocyte Homing; D011993:Recombinant Fusion Proteins; D019010:Vascular Cell Adhesion Molecule-1; D039441:Integrin alpha4; D008345:Manganese