RIP1-dependent linear and nonlinear recruitments of caspase-8 and RIP3 respectively to necrosome specify distinct cell death outcomes

There remains a significant gap in our quantitative understanding of crosstalk between apoptosis and necroptosis pathways.By employing the SWATH-MS technique,we quantified absolute amounts of up to thousands of proteins in dynamic assembling/de-assembling of TNF signaling complexes.Combining SWATH-MS-based network modeling and experimental validation,we found that when RIP1 level is below~1000 molecules/cell(mpc),the cell solely undergoes TRADD-dependent apoptosis.When RIP1 is above~1000 mpc,pro-caspase-8 and RIP3 are recruited to necrosome respectively with linear and nonlinear dependence on RIP1 amount,which well explains the co-occurrence of apoptosis and necroptosis and the paradoxical obser-vations that RIP1 is required for necroptosis but its increase down-regulates necroptosis.Higher amount of RIP1(>~46,000 mpc)suppresses apoptosis,leading to necroptosis alone.The relation between RIP1 level and occurrence of necroptosis or total cell death is biphasic.Our study provides a resource for encoding the com-plexity of TNF signaling and a quantitative picture how distinct dynamic interplay among proteins function as basis sets in signaling complexes,enabling RIP1 to play diverse roles in governing cell fate decisions.

New components of the necroptotic pathway

Programmed necrosis,also known as necroptosis,has recently drawn great attention.As an important cellular regulation mechanism,knowledge of its signaling components is expanding.Necroptosisis demonstrated to be regulated by the RIP1 and RIP3 kinases,and its pathophysiological importance has been confirmed in a number of disease models.Here we review the new members of this necroptosis pathway,MLKL,PGAM5,Drp1 and DAI,and discuss some of their possible applications according to recent findings.