TY - JOUR T1 - Palmitoylation of the Alternative Amino Terminus of the BTK-C Isoform Controls Subcellular Distribution and Signaling JF - Cancer Genomics - Proteomics JO - Cancer Genomics Proteomics SP - 415 LP - 427 DO - 10.21873/cgp.20329 VL - 19 IS - 4 AU - MOSTAFA KOKABEE AU - XIANHUI WANG AU - ELENA VOORAND AU - EDEN ALIN AU - LEILA KOKABEE AU - FAIZA KHAN AU - SOPHIA DESROSIERS AU - DOUGLAS S. CONKLIN Y1 - 2022/07/01 UR - http://cgp.iiarjournals.org/content/19/4/415.abstract N2 - Background: The alternative transcriptional isoform of Bruton’s tyrosine kinase, BTK-C, is expressed in a wide variety of epithelial tumor types where it impacts apoptosis resistance, therapeutic escape, and glucose uptake. The initial exon in BTK-C encodes a 34 amino acid extension of the amino terminus of the canonical BTK-A isoform. Its function is unknown. Materials and Methods: Site-directed mutagenesis, acylation assays and expression studies in cancer cell lines were used to determine the effects that the BTK-C first exon sequence has on kinase activity, subcellular localization and cell physiology. Analysis of BTK-C expression in tumors was conducted using genomic databases. Results: BTK-C is palmitoylated on two cysteine residues. BTK-C localization at the plasma membrane is dependent upon phosphatidylinositol 3,4,5-triphosphate (PIP3) levels as well as palmitoylation. In epithelial cancer cells, both BTK-A and BTK-C isoforms are recruited to the plasma membrane; however, BTK-A also localizes to the nucleus whereas BTK-C has a primarily perinuclear distribution. Transcription of the BTK-C isoform is inversely correlated with expression of commonly activated breast cancer signaling receptors in breast tumors. In MDA-MB-231 cells, BTK-C expression confers modest increases in proliferation and glucose uptake rates compared to BTK-A. Conclusion: Palmitoylation affects localization and regulation of BTK-C in epithelial tumor cells where it functions as an important survival factor. Expression of either palmitoylated or non-palmitoylated kinase isoforms that function in PI3K signaling may be a common regulatory feature as nine other soluble kinases in the human genome possess similarly encoded alternative N-termini (ANT). ER -