PROTEIN KINASE D REGULATES TRAFFICKING OF DENDRITIC
MEMBRANE PROTEINS IN DEVELOPING NEURONS
Bisbal, Mariano 1; Conde, Cecilia 1; Bollati, Flavia 1; Quiroga, Santiago 3;
Diaz Añel,Alberto 1,4; Malhotra, Vivek 4; Marzolo, Maria Paz 2 and
Caceres, Alfredo 1.
Diaz Añel,Alberto 1,4; Malhotra, Vivek 4; Marzolo, Maria Paz 2 and
Caceres, Alfredo 1.
Caceres, Alfredo 1.
1.1. Instituto Mercedes y Martín Ferreyra (IN/MEC-CON/CET), Córdoba,
Argentina, 2. Dep. BioI. Celular y Molecular, Fac. de Cs. Biológicas, UCC,
Chile, 3. CIQU/BIC-CONICET, Córdoba, Argentina, and 4. Department of
Biology,University of California, San Diego, La Jolla, USA.
Chile, 3. CIQU/BIC-CONICET, Córdoba, Argentina, and 4. Department of
Biology,University of California, San Diego, La Jolla, USA.
Biology,University of California, San Diego, La Jolla, USA.
Neurons are highly polarized cells typically extending several short, tip
tapering dendrites and one functional distinct long thin axon. Consistent
with their different functions, many cell membrane proteins are
preferentially distributed either to axons or dendrites, with neurons using
different and complementary mechanisms to achieve this goal. It is now
accepted that each step along the neuronal membrane trafficking pathway
-sorting into carrier vesicles, fission and exit from the Golgi, transport
along microtubules, fusion with the plasmamembrane, endocytosis and
retention at the plasma membrane- is a potential "decision site" where
molecular selectivity mechanisms could act to govern protein targeting.
The identification of proteins and/or signaling pathways that mediate
and/or control these "steps" is of key importance for understanding
neuronal polarity. Protein kinase D1 (PKD1) is a member of a novel family
of Ser-Thr kinases that regulates Golgi to cell surface protein transport. In
polarized epithelial cells inhibition of PKD1-3 activity inhibits a membrane
fission pathway specifically involved in the transport of cargo carrying
basolateral sorting signals. We now present evidence that reducing PKD 1
levels and/or activity dramatically alters the trafficking and membrane
delivery of two dendritic membrane proteins, namely the low-density
receptor-related protein (LRP) and the transferrin receptor (TfR), but not of
the axonal membrane protein L1 orVAMP2. After PKD1 suppression or
inactivation, both dendritic proteins distributed to axons and dendrites, but
are preferentially delivered to the axonal membrane, a pattern similar to
the one of axonal membrane proteins. Using Total Internal Reflection
Fluorescence Microscopy (TIRFM) and Spectral Confocal Microscopy,
after inhibition of PKD1 activity, we observed that TfR and LRP fused with
the dendritic plasma membrane, undergo rapid endocytosis, and colocalize
with VAMP2-containing vesicles. This phenotype precedes any
significant alteration in dendritic morphology. Thus, by specifying dendritic
vesicle identityPKD1 has a key role in neuronal polarity.
Supported by grants from HHMI, FONCyT, and CONICET.
