Phosphorylation of protein 4.1 on tyrosine-418 modulates its function in vitro.
Protein 4.1 was initially characterized as a protein that regulates cytoskeletal assembly in erythrocytes. However, recent studies have shown that protein 4.1 is ubiquitous in mammalian cells. Here, we show that protein 4.1 is phosphorylated on tyrosine by the epidermal growth factor receptor (EGFR) tyrosine kinase. The phosphorylation site has been localized to the 8-kDa domain, which has one tyrosine, tyrosine-418. The 8-kDa region is required for the assembly of the spectrin/actin complex, and phosphorylation by EGFR reduced the ability of protein 4.1 to promote the assembly of the spectrin/actin/protein 4.1 ternary complex. Immunoblotting with anti-phosphotyrosine antibodies showed that purified protein 4.1 contained phosphorylated tyrosine, and this increased upon phosphorylation by EGFR. This suggests that tyrosine phosphorylation of protein 4.1 occurs in vivo and may be functionally significant. The tyrosine phosphorylation site is in the center of a sequence motif that is expressed by a differentiation-specific splicing mechanism.
Subrahmanyam
G
G
Department of Pharmacology, University of Wisconsin Medical School, Madison 53706.
Bertics
P J
PJ
Anderson
R A
RA
D000199:Actins / Q000235:genetics; D000595:Amino Acid Sequence; D015153:Blotting, Western; D003598:Cytoskeletal Proteins; D066246:ErbB Receptors; D006801:Humans; D006868:Hydrolysis; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D009479:Neuropeptides; D010766:Phosphorylation; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D013049:Spectrin / Q000235:genetics; D014443:Tyrosine / Q000378:metabolism*
D000199:Actins; D003598:Cytoskeletal Proteins; D008565:Membrane Proteins; D009479:Neuropeptides; C028841:erythrocyte membrane band 4.1 protein; C120557:erythrocyte membrane protein band 4.1-like 1; D013049:Spectrin; D014443:Tyrosine; D066246:ErbB Receptors; D011505:Protein-Tyrosine Kinases