The majority of G protein-coupled receptors (GPCRs) self-assemble in the form dimeric/oligomeric complexes along the plasma membrane. Due to the molecular interactions they participate, GPCRs can potentially provide the framework for discriminating a wide variety of intercellular signals, as based on some kind of combinatorial receptor codes. GPCRs can in fact transduce signals from the external milieu by modifying the activity of such intracellular proteins as adenylyl cyclases, phospholipases and ion channels via interactions with specific G-proteins. However, in spite of (...) the number of cell functions they can actually control, both GPCRs and their associated signal transduction pathways are extremely well conserved, for only a few alleles with null or minor functional alterations have so far been found. This would seem to suggest that, beside a mechanism for DNA repairing, there must be another level of quality control that may help maintaining GPCRs rather stable throughout evolution. We propose here receptor oligomerization to be a basic molecular mechanism controlling GPCRs redundancy in many different cell types, and the plasma membrane as the first hierarchical cell structure at which selective categorical sensing may occur. Categorical sensing can be seen as the cellular capacity for identifying and ordering complex patterns of mixed signals out of a contextual matrix, i.e., the recognition of meaningful patterns out of ubiquitous signals. In this context, redundancy and degeneracy may appear as the required feature to integrate the cell system into functional units of progressively higher hierarchical levels. (shrink)

Germ cells are cross-roads of development and evolution. They define the origin of every new generation and, at the same time, represent the biological end-product of any mature organism. Germ cells are endowed with the following capacities: to store a self-descriptive program, to accumulate a protein-synthesizing machinery, and to incorporate enough nourishment to sustain embryonic development. To accomplish this goal, germ cells do not simply unfold a pre-determined program or realize a sole instructive role. On the contrary, due to the (...) complexity of their cytoarchitecture and the nature of the soma-to-germ interactions, they are heavily involved in processes of sign recognition and meaningful tissue exploration. At each stage of their inward migration, germ plasma membranes act as semiotic interfaces allowing cells to interact with the surrounding extracellular milieu and experience the compatibility of selected developmental sequences. The question of which signaling pathways are activated at each developmental stage does not result from a strictly predetermined program instructing germ cell stemness. Rather, each developmental sequence is an open-ended semiotic relationship explored and gradually defined during evolution by the context-dependency of specific cell-to-cell interactions. In this way, any structural and functional novelty that has emerged in the course of germ cell interactions may be interpreted as an exaptation fixed in the species genome in response to specific environmental constraints. (shrink)

This article considers categorical perception (CP) as a crucial process involved in all sort of communication throughout the biological hierarchy, i.e. in all of biosemiosis. Until now, there has been consideration of CP exclusively within the functional cycle of perception–cognition–action and it has not been considered the possibility to extend this kind of phenomena to the mere physiological level. To generalise the notion of CP in this sense, I have proposed to distinguish between categorical perception (CP) and categorical sensing (CS) (...) in order to extend the CP framework to all communication processes in living systems, including intracellular, intercellular, metabolic, physiological, cognitive and ecological levels. The main idea is to provide an account that considers the heterarchical embeddedness of many instances of CP and CS. This will take me to relate the hierarchical nature of categorical sensing and perception with the equally hierarchical issues of the “binding problem”, “triadic causality”, the “emergent interpretant” and the increasing semiotic freedom observed in biological and cognitive systems. (shrink)

We argue that living systems process information such that functionality emerges in them on a continuous basis. We then provide a framework that can explain and model the normativity of biological functionality. In addition we offer an explanation of the anticipatory nature of functionality within our overall approach. We adopt a Peircean approach to Biosemiotics, and a dynamical approach to Digital-Analog relations and to the interplay between different levels of functionality in autonomous systems, taking an integrative approach. We then apply (...) the underlying biosemiotic logic to a particular biological system, giving a model of the B-Cell Receptor signaling system, in order to demonstrate how biosemiotic concepts can be used to build an account of biological information and functionality. Next we show how this framework can be used to explain and model more complex aspects of biological normativity, for example, how cross-talk between different signaling pathways can be avoided. Overall, we describe an integrated theoretical framework for the emergence of normative functions and, consequently, for the way information is transduced across several interconnected organizational levels in an autonomous system, and we demonstrate how this can be applied in real biological phenomena. Our aim is to open the way towards realistic tools for the modeling of information and normativity in autonomous biological agents. (shrink)