Worm Breeder's Gazette 10(1): 44

These abstracts should not be cited in bibliographies. Material contained herein should be treated as personal communication and should be cited as such only with the consent of the author.

Dauer Phosphoproteins

A. Ray and D.L. Riddle

A cyclic AMP-dependent protein kinase activity present in the 
cytosolic fraction of dauer larva extracts phosphorylates several 
endogenous proteins in vitro.  A high level of phosphorylation of a 30 
kD protein occurs only in extracts from the dauer stage.  When dauer 
larvae are placed in food (a 5% suspension of E.  coli in S-medium) 
and allowed to recover for one hour prior to extraction, 
dephosphorylation of this protein is detected in the in vitro assays.  
If dauer larvae are placed in fresh S-medium without E.  coli, then 
almost no dephosphorylation of the 30 kD protein is observed.  Hence, 
the presence of food is required to change activities in the extracts. 
Addition of excess phosphate ion in the incubation medium inhibits 
the dephosphorylation of this protein.  This suggests that a specific 
protein phosphatase activity is present in the cytosolic fraction of 
the recovering dauer extracts.  A coomasie-stained protein gel shows 
no apparent difference in the relative amount of 30 kD proteins 
present at these two stages.  The phosphatase activity in recovering 
dauer larvae appears to be different from other protein phosphatases 
that are present both in dauer larva extracts and in extracts made 
from recovering dauer larvae, because it specifically dephosphorylates 
the 30 kD phosphoprotein.  This phosphatase activity is not derived 
from E.  coli, since incubation of the dauer larvae in E.  coli for 30 
min., instead of one hour or more, does not result in 
dephosphorylation in vitro when the extracts are made in exactly the 
same way.
We have also detected a Ca++-dependent protein kinase activity, in 
the particulate fraction of extracts prepared from recovering dauer 
larvae that phosphorylates a 180 kD protein.  This activity is not 
present in the dauer larva extracts, suggesting that a membrane-bound, 
Ca++-dependent protein kinase activity increases soon after dauer 
larvae have been placed in food, at the same time the cytosolic 30 kD 
protein becomes dephosphorylated.
The proteins subject to changes in phosphorylation may play a role 
in the maintenance of the dauer stage, and the metabolic activation 
that accompanies recovery and the reinitiation of development.  These 
changes are the earliest biochemical events we have detected in 
recovering dauer larvae, and the timing roughly corresponds to the 
point when the dauers become developmentally committed to recovery (2.
5 to 3 hours before feeding begins).  Interestingly, regulation of 
intracellular pH is thought to be a key event involved in growth 
factor associated protein phosphorylation in mammals.  The 
intracellular pH in recovering dauer larvae shifts from ~6.0 in the 
dauer to ~7.3 (Wadsworth, Abstracts of 1987 C.  elegans Meeting).