point mutant CMT1A research - from Italy

[Guest guest]

Research ABSTRACT from J Cell Sci 2003 Mar 15;116(Pt 6):987-999

Alterations in the Arf6-regulated plasma membrane endosomal recycling

pathway in cells overexpressing the tetraspan protein Gas3/PMP22.

Chies R, Nobbio L, Edomi P, Schenone A, Schneider C, Brancolini C.

Dipartimento di Scienze e Tecnologie Biomediche, Sezione di Biologia,

Universita' di Udine, P.le Kolbe 4, 33100 Udine, Italy. Laboratorio

Nazionale Consorzio Interuniversitario Biotecnologie AREA Science Park,

Padriciano 99, 34142 Trieste, Italy. Dipartimento di Biologia,

Universita' di Trieste, v. Giorgieri 5, 34100 Trieste, Italy.

Dipartimento di Scienze Neurologiche e della Visione Universita' di

Genova, v. dei Toni 5, 16138 Genova, Italy. MATI Center of Excellence,

Universita' di

Udine, P.le Kolbe 4, 33100 Udine, Italy.

Growth arrest specific 3 (Gas3)/peripheral myelin protein 22 (PMP22) is

a component of the compact peripheral nerve myelin, and mutations

affecting gas3/PMP22 gene are responsible for a group of peripheral

neuropathies in humans. We have performed in vivo imaging in order to

investigate in detail the phenotype induced by Gas3/PMP22

overexpression in cultured cells. Here we show that Gas3/PMP22 triggers

the accumulation of vacuoles, before the induction of cell death or of

changes in cell spreading. Overexpressed Gas3/PMP22 accumulates into two

distinct types of intracellular membrane compartments. Gas3/PMP2

accumulates within late endosomes close to the juxtanuclear region,

whereas in the proximity of the cell periphery, it induces the formation

of actin/phosphatidylinositol (4,5)-bisphosphate (PIP(2))-positive large

vacuoles. Gas3/PMP22-induced vacuoles do not contain transferrin

receptor, but instead they trap membrane proteins that normally traffic

through the ADP-ribosylation factor 6 (Arf6) endosomal compartment. Arf6

and Arf6-Q67L co-localize with Gas3/PMP22 in

these vacuoles, and the dominant negative mutant of Arf6, T27N, blocks

the appearance of vacuoles in response to Gas3/PMP22, but not its

accumulation in the late endosomes. Finally a point mutant of Gas3/PMP22

responsible for the Charcot-Marie-Tooth 1A disease is unable to trigger

the accumulation of PIP(2)-positive vacuoles. Altogether

these results suggest that increased Gas3/PMP22 levels can alter

membrane traffic of the Arf6 plasma-membrane-endosomal recycling pathway

and show that, similarly to other tetraspan proteins, Gas3/PMP22 can

accumulate in the late endosomes.