CSM News
Electronic Edition
Volume 2, number 15
April 23, 1994

Please submit abstracts of your papers as soon as they have been
accepted for publication by sending them to CSM-News@worms.cmsbio.nwu.edu.

Back issues of CSM-News, the CSM Reference database and other useful
information is available by anonymous ftp from worms.cmsbio.nwu.edu
[129.105.233.50], via Gopher at the same address, or by World Wide Web
through www.nwu.edu.

==============
Announcements
==============

An updated version of Rich Sucgang's Dictyostelium Gene Disruption
Table is available from the archive in the directory DGDT.  

From the read.me.first file:


THE DICTY GENE DISRUPTION TABLE
This is version 2.0b

This archive contains three files, which all have the same information. 
The three are merely in different formats to accomodate different 
information management programs. These are: 

DGDT.TDF - tab delimited text
DGDT.DIF - database interchange format
DGDT.SYK - SYLK format

All of these can usually be imported by a database or spreadsheet 
program. The most universal is the tab delimited text file; some word 
processing files can also convert it into a tabular form.

A directly readable format is under construction, as well as a hard copy 
version. Would there be interest in a PostScript version of the hard copy?
For the moment, however, you need some kind of data management software 
to access this (you'll probably want one anyway).

There are 61 entries; however, the first entry is merely a description of 
what is in each of the fields. I will be revising this release shortly, 
pending corrections and responses.

Thank you everyone for your patience. Many thanks for those who informed 
me of the gene knockouts in progress, and particularly to Rex Chisholm 
for maintaining the ftp site, and just being very nice.

Please refer to the file DGDTSPEC.TXT for the information I request for 
an entry into the table. I hope people find this useful, and I look 
forward to your responses.

Richard Sucgang
rs54@columbia.edu


==========
Abstracts
==========

THE CLATHRIN HEAVY CHAIN FUNCTIONS IN SORTING AND SECRETION OF
LYSOSOMAL ENZYMES IN DICTYOSTELIUM DISCOIDEUM.

Tracy Ruscetti*, James A. Cardelli*,# Maria L. Niswonger+, and Theresa
J.  O'Halloran+

*Department of Microbiology and Immunology, Louisiana State University
Medical Center, Shreveport, LA 71130 +Department of Cell Biology, Duke
University Medical Center, Durham, NC 27710

J. Cell Biol., in press

Summary

   The clathrin heavy chain is a major component of clathrin-coated
vesicles that function in selective membrane traffic in eukaryotic
cells.  We disrupted the clathrin heavy chain gene (chcA) in
Dictyostelium discoideum to generate a stable clathrin heavy
chain-deficient cell line.  Measurement of pinocytosis in the
clathrin-minus mutants revealed a 4-5 fold deficiency in the
internalization of fluid-phase markers.  Once internalized, these
markers recycled to the cell surface of mutant cells at wild-type
rates.  We also explored the involvement of clathrin heavy chain in
the trafficking of lysosomal enzymes.  Pulse chase analysis revealed
that clathrin-minus cells processed most alpha-mannosidase to mature
forms, however, approximately 20-25% of the precursor molecules
remained uncleaved, were missorted, and were rapidly secreted by the
constitutive secretory pathway.  The remaining intracellular
alpha-mannosidase was successfully targeted to mature lysosomes.
Standard secretion assays showed that the rate of secretion of
alpha-mannosidase was significantly less in clathrin-minus cells
compared to control cells in growth medium.  Interestingly the
secretion rates of another lysosomal enzyme, acid phosphatase, were
similar in clathrin-minus and wild-type cells.  Like wild-type cells,
clathrin-minus mutants responded to starvation conditions with
increased lysosomal enzyme secretion.  Our study of the mutant cells
provide in vivo evidence for roles for the clathrin heavy chain in (i)
the internalization of fluid from the plasma membrane, (ii) sorting of
precursor hydrolases from the constitutive secretory pathway to the
lysosomal pathway, and (iii) secretion of mature hydrolyases from the
lysosome to the extracellular space.

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[End CSM-News, volume 2, number 15]