LAPTM4B facilitates late endosomal ceramide export to control cell death pathways.

Abstract

Lysosome-associated protein transmembrane-4b (LAPTM4B) associates with poor prognosis in several cancers, but its physiological function is not well understood. Here we use novel ceramide probes to provide evidence that LAPTM4B interacts with ceramide and facilitates its removal from late endosomal organelles (LEs). This lowers LE ceramide in parallel with and independent of acid ceramidase-dependent catabolism. In LAPTM4B-silenced cells, LE sphingolipid accumulation is accompanied by lysosomal membrane destabilization. However, these cells resist ceramide-driven caspase-3 activation and apoptosis induced by chemotherapeutic agents or gene silencing. Conversely, LAPTM4B overexpression reduces LE ceramide and stabilizes lysosomes but sensitizes to drug-induced caspase-3 activation. Together, these data uncover a cellular ceramide export route from LEs and identify LAPTM4B as its regulator. By compartmentalizing ceramide, LAPTM4B controls key sphingolipid-mediated cell death mechanisms and emerges as a candidate for sphingolipid-targeting cancer therapies.

• Authors: Tomas Blom, Shiqian Li, Andrea Dichlberger, Nils Bäck, Young Ah Kim, Ursula Loizides-Mangold, Howard Riezman, Robert Bittman, Elina Ikonen
• Journal: Nature chemical biology (Nat Chem Biol) Vol. 11 Issue 10 Pg. 799-806 (Oct 2015) ISSN: 1552-4469 [Electronic] United States
• PMID: 26280656 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Anthracyclines
• Antineoplastic Agents
• Ceramides
• LAPTM4B protein, human
• Membrane Proteins
• Oncogene Proteins
• RNA, Small Interfering
• Sphingomyelins
• Paclitaxel

Topics

• Anthracyclines (pharmacology)
• Antineoplastic Agents (pharmacology)
• Apoptosis (drug effects, physiology)
• Biological Transport
• Cell Line, Tumor
• Ceramides (metabolism)
• Endosomes (metabolism)
• Gene Silencing
• Humans
• Intracellular Membranes (metabolism)
• Membrane Proteins (genetics, metabolism)
• Oncogene Proteins (genetics, metabolism)
• Paclitaxel (pharmacology)
• Protein Binding
• RNA, Small Interfering (genetics)
• Sphingomyelins (metabolism)