Abstract
In recent years, “raft hypothesis”, in which hypothetical membrane domains, called lipid raft domains, might act as platforms where signaling molecules are assembled for their interactions and functions in/on the plasma membrane. Using single–molecule tracking, we have found such domains are only formed on–demand upon stimulation–induced clustering of receptors that can be associated with raft domains. Furthermore, signaling molecules are recruited to such induced rafts transiently (of the order of 0.1 s). Therefore, in this review, we propose that raft–related bulk intracellular signals that tend to last over 1000 s might be pulse coded or frequency modulated by the pulse–like digital activation of individual molecules, and that the intensity of the bulk signal might mainly be determined by the number of pulses at a given time. Such on–demand rafts are considered to be involved in bovine spongiform encephalopathy development, HIV infection, and Alzheimer disease pathogenesis, and this finding sheds new light on these processes.
