LTK
Function
Receptor with a tyrosine-protein kinase activity (PubMed:10445845, PubMed:20548102, PubMed:30061385). Following activation by ALKAL1 or ALKAL2 ligands at the cell surface, transduces an extracellular signal into an intracellular response (PubMed:30061385, PubMed:34646012). Ligand-binding to the extracellular domain induces tyrosine kinase activation, leading to activation of the mitogen-activated protein kinase (MAPK) pathway (PubMed:20548102). Phosphorylates almost exclusively at the first tyrosine of the Y-x-x-x-Y-Y motif (By similarity). The exact function of this protein is not known; studies with chimeric proteins demonstrate its ability to promote growth and specifically neurite outgrowth, and cell survival (PubMed:18849880, PubMed:9223670). Involved in regulation of the secretory pathway involving endoplasmic reticulum (ER) export sites (ERESs) and ER to Golgi transport (PubMed:20548102).
Involvement in disease
Genetic variations in LTK that cause up-regulation of the PI3K pathway may possibly contribute to susceptibility to abnormal proliferation of self-reactive B-cells and, therefore, to systemic lupus erythematosus (SLE) (PubMed:14695357). SLE is a chronic, inflammatory and often febrile multisystemic disorder of connective tissue, thought to represent a failure of the regulatory mechanisms of the autoimmune system (PubMed:14695357).
Post-translational modifications
Phosphorylated at tyrosine residues by autocatalysis, which activates kinase activity.
Sequence Similarities
Belongs to the protein kinase superfamily. Tyr protein kinase family. Insulin receptor subfamily.
Tissue Specificity
Expressed in non-hematopoietic cell lines and T- and B-cell lines.
Cellular localization
- Cell membrane
- Single-pass type I membrane protein
Alternative names
TYK1, LTK, Leukocyte tyrosine kinase receptor, Protein tyrosine kinase 1