LZTR1 is a melanoma oncogene that promotes invasion and suppresses apoptosis

Leucine zipper like transcription regulator 1 (LZTR1) is amplified in acral melanomas, is required for melanocytes and melanoma cell proliferation, and it induces anchorage-independent growth, by yet unknown mechanisms. We therefore performed comprehensive studies to identify its activity in melanomas employing proximity biotinylation and co-immunoprecipitation combined with LC-MS/MS proteomics and molecular characterization. The results show that LZTR1 regulates the ubiquitin proteasome system in melanoma cells and also associates with actin-related proteins and actin cytoskeleton organization. Its downregulation suppresses the protective effect of the autophagy-initiating ULK1 and AMBRA1, regulators of normal cell survival and proliferation, and upregulates the sequestosome 1 (SQSTM1/p62), an autophagic cargo adapter which mediates selective degradation of ubiquitinated proteins. In contrast, overexpression of LZTR1 provides growth advantage under environmental stress, enhancing cell invasion, by activating ERBB3 receptor and its downstream targets PYK2 and SRC tyrosine kinases that regulate the cytoskeleton, actin organization, cell spreading, cell migration and adhesion. LZTR1 is a "safeguard" for melanoma cells under stress and its downregulation can be exploited for melanoma therapy.