Tyrosine phosphorylation at a site highly conserved in the L1 family of cell adhesion molecules abolishes ankyrin binding and increases lateral mobility of neurofascin.
This paper presents evidence that a member of the L1 family of ankyrin-binding cell adhesion molecules is a substrate for protein tyrosine kinase(s) and phosphatase(s), identifies the highly conserved FIGQY tyrosine in the cytoplasmic domain as the principal site of phosphorylation, and demonstrates that phosphorylation of the FIGQY tyrosine abolishes ankyrin-binding activity. Neurofascin expressed in neuroblastoma cells is subject to tyrosine phosphorylation after activation of tyrosine kinases by NGF or bFGF or inactivation of tyrosine phosphatases with vanadate or dephostatin. Furthermore, both neurofascin and the related molecule Nr-CAM are tyrosine phosphorylated in a developmentally regulated pattern in rat brain. The FIGQY sequence is present in the cytoplasmic domains of all members of the L1 family of neural cell adhesion molecules. Phosphorylation of the FIGQY tyrosine abolishes ankyrin binding, as determined by coimmunoprecipitation of endogenous ankyrin and in vitro ankyrin-binding assays. Measurements of fluorescence recovery after photobleaching demonstrate that phosphorylation of the FIGQY tyrosine also increases lateral mobility of neurofascin expressed in neuroblastoma cells to the same extent as removal of the cytoplasmic domain. Ankyrin binding, therefore, appears to regulate the dynamic behavior of neurofascin and is the target for regulation by tyrosine phosphorylation in response to external signals. These findings suggest that tyrosine phosphorylation at the FIGQY site represents a highly conserved mechanism, used by the entire class of L1-related cell adhesion molecules, for regulation of ankyrin-dependent connections to the spectrin skeleton.
Garver
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TD
Howard Hughes Medical Institute, Duke University Medical Center, Durham, North Carolina 27710, USA.
Ren
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Q
Tuvia
S
S
Bennett
V
V
D000595:Amino Acid Sequence; D000818:Animals; D017487:Ankyrins / Q000378:metabolism*; D015815:Cell Adhesion Molecules / Q000378:metabolism*; D015816:Cell Adhesion Molecules, Neuronal / Q000378:metabolism; D003902:Detergents / Q000737:chemistry; D006873:Hydroquinones / Q000494:pharmacology; D008560:Membrane Fluidity; D008969:Molecular Sequence Data; D009414:Nerve Growth Factors / Q000378:metabolism* / Q000494:pharmacology; D019000:Phosphotyrosine / Q000378:metabolism*; D011485:Protein Binding; D017027:Protein Tyrosine Phosphatases / Q000378:metabolism; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D051381:Rats; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D012995:Solubility
D017487:Ankyrins; D015815:Cell Adhesion Molecules; D015816:Cell Adhesion Molecules, Neuronal; D003902:Detergents; D006873:Hydroquinones; D009414:Nerve Growth Factors; C504594:Nfasc protein, rat; C084037:dephostatin; D019000:Phosphotyrosine; D011505:Protein-Tyrosine Kinases; D017027:Protein Tyrosine Phosphatases