Structural studies showed that activation of RIPK3 by RIPK1 involves the formation of a functional hetero-oligomeric amyloidal signaling complex that mediated programmed necrosis (Li J et al. 2012; Mompean M et al. 2018). The RIP homotypic interaction motifs (RHIMs) of RIPK1 and RIPK3 were found to mediate the assembly of these heterodimeric filamentous structures (Li J et al. 2012). RIPK1 was reported to control RIPK3 oligomerization in both postive and negative manners (Orozco S et al. 2014). RIPK3 recruitment to other RIPK3 protomers within this assembly may be favored by allosteric interactions between their kinase domains and activation by autophosphorylation of a site in the C-lobe of their kinase domains (Raju S et al. 2018). Presumably this autophosphorylation leads to an electrostatic repulsion or conformational change that disfavors RIPK3 hetero-oligomer formation to allow RIPK3 to preferentially self-associate within the necrosome complex. Owing to the size and the toxicity arising from overexpressing RIPK1 and RIPK3 in cells, this has been problematic to study in detail. The underlying mechanism is still debated, but RIPK3 transphosphorylation is believed to be crucial for MLKL activation (Orozco S et al. 2014; Cook WD et al. 2014).
Hsiao, YS, McQuade, T, Wu, H, Chan, FK, Li, J, Walz, T, Siemer, AB, Moriwaki, K, McDermott, A, Moquin, D, Damko, E, Napetschnig, J
Bozkurt, G, Li, W, McDermott, AE, Wu, H, Mompeán, M, Li, J, Siemer, AB, Laage, S
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