Table 2.

Normalized ErbB2 distribution with or without trastuzumab or GA

			Endosomes and lysosomes
	Endocytic (% of NB)	Tubulovesicular (% of endocytic)	Internal mb (% of endocytic)	Limiting mb (% of endocytic)	Coated limiting endosomal mb (% of limiting mb)
Untreated	10.2 ± 1.9	86.1 ± 3.7	6.1 ± 1.8	5.4 ± 2.2	0 ± 0
+T, 0 min	11.6 ± 1.6	79.8 ± 5.8	7.4 ± 2.8	12.2 ± 5.6	0 ± 0
+T, 5 min	13.0 ± 1.9	78.7 ± 4.8	9.0 ± 3.7	3.4 ± 1.7	0 ± 0
+T, 3 h	16.6 ± 2.6	70.5 ± 3.2	15.1 ± 3.0	10.3 ± 2.6	4.2 ± 3.7
+GA, T, 3 h	41.2 ± 3.7a	33.0 ± 5.7a	54.5 ± 5.8a	11.9 ± 2.6	37.9 ± 9.1a
+GA, 3 h	37.2 ± 3.9a	45.5 ± 5.8a	41.4 ± 7.9a	11.5 ± 3.5	14.3 ± 12.0

SKBr3 cells ± surface-bound trastuzumab (T) were incubated at 37°C ± GA (G) as indicated and then fixed and processed for quantitative detection of ErbB2 by immunogold electron microscopy as described in Materials and Methods. Normalization to the number of total non-biosynthetic (NB) (left column), endocytic (middle three columns), or endosomal limiting membrane localized gold particles was performed for each cell profile individually prior to mean and SE calculations. Not included is a small population of endocytic and undefined 60-150-nm vesicles comprising <5% of the intracellular label. Non-normalized data are presented in Supplementary Table 2. Qualitatively similar results were observed for BT474 cells (unpublished data). NB, non-biosynthetic; mb, membrane; T, trastuzumab; GA, geldanamycin.

^ap < 0.01, in comparison with corresponding +T, 3-h result.