ASIC subunit ratio and differential surface trafficking in the brain

Table 1 A simplified prediction (assuming homogenous distribution of ASICs within a region) of the relative proportion of ASIC1a homomers, 1a:2a heteromers and 2a homomers in different brain regions

Relative % of ASIC subunits	OB	Cx	Hp	STR	Am	Cb	BS
ASIC1a	57.4 %	62.2 %	54.3 %	80.1 %	65.0 %	76.8 %	73.9 %
ASIC1b	26.6 %	23.0 %	24.1 %	14.6 %	22.2 %	4.3 %	19.3 %
ASIC1c	16.0 %	14.9 %	21.7 %	5.3 %	12.8 %	19.0 %	6.7 %
Relative & of functional ASICs
1a:1a:1a	31.9 %	38.9 %	33.2 %	60.5 %	41.5 %	85.0 %	49.8 %
1a:1a:2a	44.4 %	43.2 %	44.2 %	33.1 %	42.4 %	14.2 %	39.1%
1a:2a:2a	20.5 %	16.0 %	19.6 %	6.0 %	14.5 %	0.8 %	10.2 %
2a:2a:2a	3.2 %	2.0 %	2.9 %	0.4 %	1.6 %	0.0 %	0.9 %

Top three rows are the percentage of 1a, 2a and 2b subunits, based on Fig. 4. The lower four rows are the proportion of 1a homomers and 1a:2a heteromers. The proportions are calculated based on total protein expression and assuming a random assembly of ASIC subunits into trimers [25]. Since we detected little ASIC2b at cell surface in the brain, we did not include ASIC2b-containg complexes in this table for simplicity. Initial percentage was calculated as follows
1a homomer = %1a × %1a × %1a
2a homomer = %2a × %2a × %2a
1a: 2a heteromer (2:1 ratio) = %1a × %1a × %2a × 3
1a:2a heteromer (1:2 ratio) = %1a × %2a × %2a × 3
To calculate the relative percentage of each of the four trimers, the raw percentage was then divided by the total percent of the four trimers.

ISSN: 1756-6606