# INTRACELLULAR PROCESSING OF MARCROMOLECULAR CONJUGATES

> **NIH NIH R01** · UNIVERSITY OF SOUTHERN CALIFORNIA · 1987 · $97,953

## Abstract

Drug-carrying proteins transported into cells by endocytosis can
have marked pharmacologic effects, provided active drug is
released inside cells.  They are excellent tools, therefore, to study
the intracellular processing of macromolecules.  This project will
compare drug conjugates using the same drug (methotrexate,
MTX) but differing either in their carrier or in their linkage of
drug to carrier.  Two non-degradable drug carriers will be used,
i.e., poly(D-lysine) internalized by non-specific endocytosis, and
anti-TNP:MTX-TNP-poly(D-homocitrulline) immune complexes
internalized by Fc-receptor-mediated endocytosis.  The linkages
can be tailored so as to cleave in three different cellular
environments.  They will include a triglycine linkage cleaved by
lysosomal proteases, an acid-sensitive cis-aconityl linkage
hydrolysed in acidic intracellular organelles, and a disulfide
linkage cleaved wherever reducing conditions prevail along the
endocytotic pathway.  The conjugates will be used to characterize
these three intracellular compartments, especially the third,
about which least is known.  The compartments will be identified
by subcellular fractionation following exposure of cells to
conjugates containing 3H-MTX and 14C-labeled carriers.  Since
released drugs will diffuse out of organelles, a decrease in the
3H/14C-ratio will identify the fractions in which cleavage is
taking place.  Factors known to influence these intracellular
functions (inhibitor of proteases, lysosomotropic amines,
precursors and inhibitors of glutathion synthesis) will be tested for
their effect on both the intracellular distribution of 3H-MTX and
the cytotoxicity of the conjugate.  The same MTX-linkages will be
inserted in two further carriers which follow different
endocytotic pathways, namely transferrin, and a monoclonal
antibody against the SSEA-1 tumor antigen.  The fate of tumor
antigen-antibody complexes is largely unknown and will be
clarified by comparison with that of known ligands.  Defects in
endocytotic functions have been associated with important
diseases (atherosclerosis, storage diseases).  This research will
provide new information on the intracellular processing of
macromolecules in endocytosis.  It will also yield basic
information on mechanisms of drug release from macromolecular
carriers, including carriers that are selectively targeted to tumor
cells.

## Key facts

- **NIH application ID:** 3172628
- **Project number:** 7R01CA034798-05
- **Recipient organization:** UNIVERSITY OF SOUTHERN CALIFORNIA
- **SAM.gov UEI:** G88KLJR3KYT5
- **Principal Investigator:** WEI-CHIANG SHEN
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 1987
- **Award amount:** $97,953
- **Award type:** 7
- **Project period:** 1987-07-01 → 1990-11-30

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/3172628

## Citation

> US National Institutes of Health, RePORTER application 3172628, INTRACELLULAR PROCESSING OF MARCROMOLECULAR CONJUGATES (7R01CA034798-05). Retrieved via MORVS 2026-10-25 from https://api.morvs.ai/grant/nih/3172628. Licensed CC0.

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