Characterization of MARCKS (myristoylated alanine-rich C kinase substrate)identified by a monoclonal antibody generated against chick embryo neural retina

To identify molecular markers of cell differentiation in developing nervous tissue, monoclonal antibodies against chick embryo neural retina were made . One of them, 3C3mAb, recognized a developmentally regulated antigen prese nt in several organs of the CNS. Data from MALDI-TOF mass spectrometry and peptide sequencing of the immuno-affinity purified protein indicated identi ty of the antigen with MARCKS. The immunoreactive material was always found as a unique polypeptide (M-r 71 kDa) in SDS-PAGE, however isoelectrofocusi ng revealed the existence of several bands (pI ranging from 4.0 to 4.5). In terestingly some retinal cell types, as photoreceptors, exhibited an extrem ely significant decrease in the intensity of the immunoreactive material du ring the final phases of terminal differentiation while others, as some ret inal neurons, maintained the immunoreactivity when fully differentiated. Ta ken together these results indicate that MARCKS, a protein susceptible of s everal posttranslational modifications as myristoylation and phosphorylatio n at variable extent, may act differently in neural retina cell types. (C) 1999 Academic Press.