Regulation of cell fate by lymphotoxin (LT) receptor signalling: Functional differences and similarities of the LT system to other TNF superfamily (TNFSF) members

The role of TNFR family members in regulating cell fate both in the immune system and in non-lymphoid tissues has been under extensive research for decades. Moreover, the ability of several family members (death receptors) to induce death (mainly via apoptosis) represents a promising target for cancer therapy. Many studies have focused mostly on death receptors such as TNFRI, Fas and TRAIL-R due to their strong pro-apoptotic potential. Yet, cell death can be triggered via non-classical death receptors, and the Lymphotoxin (LT) system represents a very good example of such a TNFR subfamily. Here we provide a comprehensive review of intracellular signalling pathways and cellular responses to LTspecific signalling, and compare for the first time the LT system to other TNFRs, such as CD40. Our aim is to highlight that non-classical TNFR-TNFL dyads such as the LT system demonstrate more complex, cell-type and context-specific capabilities. Understanding these complexities will permit a better understanding of the biological mechanisms via which nondeath domain-containing TNFRs induce cell death, but may also allow the design of better therapeutic strategies.