Received for publication January 18, 2007.
Revised August 14, 2007.
Accepted for publication August 16, 2007.

MiTMAB and OcTMAB are surface-active small molecule dynamin inhibitors that block endocytosis mediated by dynamin I or dynamin II

Abstract

Dynamin is a GTPase enzyme involved in membrane constriction and fission during endocytosis. Phospholipid binding via its pleckstrin homology (PH) domain maximally stimulates dynamin activity. We developed a series of surface-active small molecule inhibitors, such as myristyl trimethyl ammonium bromide (MiTMAB) and octadecyltrimethyl ammonium bromide (OcTMAB), and now show MiTMAB targets the dynamin-phospholipid interaction. MiTMAB inhibited dynamin GTPase activity with a Ki of 940 ± 25 nM. It potently inhibited receptor mediated endocytosis (RME) of transferrin or epidermal growth factor (EGF) in a range of cells without blocking EGF binding, receptor number or autophosphorylation. RME inhibition was rapidly reversed after washout. The rank order of potency for a variety of MiTMAB analogues on RME matched the rank order for dynamin inhibition, suggesting dynamin recruitment to the membrane is a primary cellular target. MiTMAB also inhibited synaptic vesicle endocytosis (SVE) in rat brain nerve terminals (synaptosomes) without inducing depolarization or morphological defects. Therefore the drug rapidly and reversibly blocks multiple forms of endocytosis with no acute cellular damage. MiTMAB's unique mechanism of action provides an important tool to better understand dynamin-mediated membrane trafficking events in a variety of cells.

Key words: Receptor synthesis/trafficking, Recycling, Immunocytochemistry, Enzymology, Anti-psychotics, Exocytosis, Synaptic plasticity