Can regulatory peptides be regarded as words of a biological language

Despite the complexities of individual systems, neurocrine, endocrine, and growth factor-mediated signaling systems show striking similarities in the molecules they use for communication and in their signal-transduction mechanisms. In contrast to the traditional view in cell biology, which has focused on the regulatory aspects of neurocrine and endocrine messengers and growth factors, an analysis of various aspects of peptidergic cell-to-cell communication on the basis of information theory is suggested. According to theorems for efficient and error-free encoding, the differences in rate and distance of information transfer and in noise interference between neurocrine, endocrine, and growth factor-mediated messages require different encoding strategies. These differences are reflected in the use of plurichemical transmission (to increase information content) or in the number and sequence of amino acids within peptide molecules (to protect against noise interference). In contrast to the quantitative information content, the qualitative information of the messages is not transmitted but is retrieved when the message interacts with transduction networks at the receiver cell. The semantic information is contained within the rules specifying the conditional co-occurrences of signals. The suggested analysis provides a framework for the understanding of various aspects of cell-to-cell communication, such as structure-function relationship of regulatory peptides, multiple receptor subtypes, plurichemical transmission, and transduction networks. The data discussed are consistent with the role of regulatory peptides as signals in a universal structured code for biological communication.