Neuronal Functions Associated with Endo- and Exocytotic Events-cum-Molecular Trafficking may be Cell Maturation-Dependent: Lessons Learned from Studies on Botulism

Abstract

The passion in the scientific endeavors of Marshall Warren Nirenberg had been his quest for knowledge regarding the storage, retrieval, and processing of information in the cell. After deciphering the genetic code for which he shared the Nobel Prize in Physiology and Medicine in 1968, Nirenberg devoted his attention to unraveling the mysteries in the most complex cellular organization in the body, i.e., the nervous system, especially those governing neuronal development, plasticity, and synaptogenesis. During the tenure of the primary author (RR) as a postdoctoral Staff Fellow in the Nirenberg laboratory in the late seventies to early eighties, he had the opportunity of working on projects related to what Nirenberg used to broadly define as the "synaptic code." The major aspects of these projects dealt with the functional macromolecules relevant to neuronal growth, organization, lineage, selectivity, stabilization, synaptogenesis, and functions such as neuroexocytosis. This author's emphasis was particularly on voltage-gated calcium channels that regulate stimulus-induced neurotransmitter release. One central as well as crucial theme in these studies was the fact that the neurons had to be mature and differentiated in order to study these entities (Science 222: 794-799, 1983; Cold Spring Harb Symp Quant Biol 48: 707-715, 1983). In this communication, we illustrate how did this basic knowledge, i.e., cell maturation-dependent properties being essential for neuronal functions, led to a successful experimental design and demonstration of the validity of the targeted neurologic therapeutic delivery approach based on recombinant botulinum toxin serotype A (BoNT/A) heavy chain (rHC) serving as a neuron-specific targeting molecule (BMC Pharmacol 9: 12, 2009).

Morphological and functional differentiation in BE(2)-M17 human neuroblastoma cells by treatment with Trans-retinoic acid

“…It has been shown here as well as in other studies that maturation of neuronal cultures is very important when studying the effects of toxicants [17]. It is known that intracellular Ca 2+ is highly regulated and involved in normal cell functions and in toxicological mechanisms.…”

“…The treatment of M17 with RA for a minimum of 72 hrs may be essential for functional neuronal cultures. It has been postulated that neuronal functions are cell maturation dependent [17]. …”

“…In our and other laboratories, Ca 2+ -dependent [ 3 H] glycine release inhibition due neurotoxins (e.g. botulinum neurotoxins and tetanus toxin) has been shown to be a sensitive indicator of toxicity in neuronal models such as cultured primary mouse spinal cord cells [15-17] and synaptosomes prepared from rat brain and spinal cord [18]. We have also looked at the effects of RA differentiation on M17 cells toxicity studies of the known toxicant, phosgene (CG, COCl 2 ).…”