Protein 1a: a major wheat germ agglutinin binding protein on the surface of human granulocytes associated with the cytoskeleton.

Lectin-receptors on leukocyte and endothelial surfaces are becoming more important in the light of increasing evidence which implicates lectin-carbohydrate interactions in diverse physiological phenomena. This study reports the identification of a major 118 kDa granulocyte surface protein, (Protein 1 a) which binds the lectin wheat germ agglutinin (WGA), and is distinctly different from reported WGA binding granulocyte membrane proteins. Protein 1 a has been isolated from the Triton-soluble and Triton-insoluble lysates of normal individuals and patients with Chronic Myeloid Leukemia (CML) using a combination of differential solubilization, lectin affinity, ion exchange chromatography and HPLC. The protein from the detergent lysates of both normal and CML granulocytes has similar pI values, lectin affinities, and hydrophobicity. However, its solubility in Triton is different in the two cell types. In 71% of CML cases examined, Protein 1 a exhibits decreased Triton solubility suggesting its increased association with the cytoskeleton (CSK). Stimulation of normal granulocytes with WGA leads to the translocation of the soluble form of Protein 1 a to the Triton-insoluble fraction. This cytoskeletal recruitment of Protein 1 a is sustained only under conditions of excess WGA and occupied receptor. The CSK disruptive agent dihydrocytochalasin B (H2CB) releases the insoluble form of the receptor into the Triton-soluble fraction. Investigation of a CSK-involving process such as ligand internalization revealed that CML granulocytes exhibit slower kinetics of internalization of fluorescent WGA molecules.(ABSTRACT TRUNCATED AT 250 WORDS)