known function that is expressed during neuronal 
sprouting (both de novo and during regeneration). 
Both p38 and p34 are intimately associated with 
GCP membranes (as they partition into the deter- 
gent phase after TX-114 extraction), and their rela- 
tive abundance provided sufficient amounts for gas- 
phase protein microsequencing (in collaboration 
with Dr. Clive A. Slaughter, HHMI, University of 
Texas Southwestern Medical Center at Dallas). Mul- 
tiple tryptic peptides from each protein were se- 
quenced and revealed that p38 and p34 corre- 
spond to the a- and (3-subunits of G proteins, 
respectively. This identification was confirmed for 
each by the use of subu nit-specific antipeptide anti- 
bodies (courtesy of Dr. Alfred G. Gilman, University 
of Texas Southwestern Medical Center at Dallas). 
Thus the major polypeptides associated with GCP 
membranes (pp46/GAP-43, p38/G^, or p34/Gp) are 
peripheral proteins associated with the cytoplasmic 
surface of the neuronal plasmalemma, not integral 
membrane proteins. Larger scale biochemical prep- 
arations of GCP membranes, together with immu- 
nological strategies, will be required to identify 
other more minor components. 
To complement these biochemical studies of 
nerve growth cone membranes. Dr. Ellis and his 
colleagues have initiated a second approach to 
PUBLICATIONS 
identify genes expressed at the onset of neural 
sprouting. In collaboration with Dr. Hammer, a re- 
porter gene (bacterial p-galactosidase) linked to the 
weak herpes simplex virus thymidine kinase pro- 
motor (i.e., a promotor devoid of tissue-specific ele- 
ments and therefore subject to positional effects) 
has been introduced into the germline of trans- 
genic mice to mark areas of active transcription dur- 
ing different stages of mouse development. Histo- 
logical examination of whole fetuses and sections 
of transgenic offspring at different stages of embry- 
onic and fetal development identify those lines that 
express the reporter gene in areas of interest in the 
central nervous system at the time of neuronal 
sprouting. The DNA of the transgene (of viral/bacte- 
rial origin) will be used for cloning of the flanking 
regions of host mouse DNA for the characterization 
of the enhancer elements and structural genes 
interrupted by the integration event. This strategy 
complements the study of the GCP and obvi- 
ates the limitations of protein quantity or antigenic- 
ity inherent in a biochemical/immunological ap- 
proach. 
Dr. Ellis is also Assistant Professor of Bio- 
chemistry at the University of Texas Southwestern 
Medical Center at Dallas. 
Books and Chapters of Books 
Ellis, L., Sissom, J., Schaefer, E., McDonald, N., and Blundell, T. 1989. Molecular genetic approaches for 
studying the interaction of insulin and its receptor. In Diabetes 1988 (Larkins, R.G., Zimmet, PZ., and 
Chisholm, D.J., Eds.). Amsterdam: Elsevier, pp 513-516. 
Articles 
Ramos, P, and Ellis, L. 1989- Expression in heterologous cells of the unusual cytoplasmic domain of rat brain 
5B4/NCAM-ld. Mol Brain Res 6:61-68. 
Ramos, E , Safaei, R., Kayalar, C, and Ellis, L. 1989. Isolation and sequence of Xgtll cDNA clones encoding 
the 5B4 antigen expressed on sprouting neurons. Mol Brain Res 5:297-303. 
Simkowitz, P, Ellis, L., and Pfenninger, K.H. 1989. Membrane proteins of the nerve growth cone and their de- 
velopmental regulation./ A'^eMrosc/ 9:1004-1017. 
Sissom, J. , and Ellis, L. 1989. Secretion of the extracellular domain of the human insulin receptor from insect 
cells by use of a baculovirus vector. Biochem J 261:119-126. 
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