International AIDS Society

HIV protease inhibitors and mammalian proteasomes: what's that got to do with pneumocystis?

Mazza F.¹, Valerio A.¹, Tronconi E.¹, Groettrup M.², Kremer M.², Cargnel A.¹, Rizzardini G.³, Atzori C.¹

Objectives: Besides the antiviral effect, HIV PIs showed in vitro anti-opportunistic and metabolic effects possibly linked to proteasome modulation. Pneumocystis (Pc) in vitro growth is inhibited by PIs, except ATV. This study evaluate the PIs activity on proteasome of HEL299 (Pc feeder cells), U937 and Jurkat cell lines.
Methods: Intact cells and HEL299 purified 20S proteasome, exposed or unexposed to PIs at clinically relevant dosages, were submitted to fluorometric assay detecting the chymotrypsin-like activity. Lactacystin and Bortezomib were used as positive control. A 2-way ANOVA test and the Bonferroni correction as a post-hoc test were used.
Results: HEL299 proteasome activities are expressed as percentage of untreated control (Table); *p<0.05, **p<0.01, ***p<0.001.

	Purified 20S	Intact cells
LPV (mM) 0.16-0.8-8-16	72-42-54-62	71*-53-50-40*
SQV (mM) 15-30	80-33	55*-41*
ATV (mM) 0.014-0.14-1.4	183-236-209	133*-156-144**
TPV (mM) 0.35-0.7-3.5-7	99-101-82-72	231*-285-151-156*

LPV inhibited proteasome in Jurkat (98-62***-73*-45*** %) and in U937 (81**-81**-61***-43*** %) cells. Otherwise, 1.4 µM ATV caused an increase of activity (131*** % in Jurkat, 152*** in U937).
Conclusions: LPV and SQV-related inhibition of proteasome is possibly due to their competitive bond at the enzyme active site. The ATV opposite behaviour could be caused to its peculiar structure modulating a site distinct from the catalytic. TPV produced an inhibition of purified proteasome, followed by an activation in intact cells, possibly due to an over-expression of proteasome genes in response to the farmacological inhibition. These results are consistent with the PIs-related modulation of Pc in vitro growth. The in vitro ATV pro-opportunistic behaviour is connected with non hyperlipemia induction occurring in patients treated with other PIs. Therefore, it seems necessary investigate more in details how PIs-associated modulation of proteasome with basic cellular biology.

4th IAS Conference on HIV Pathogenesis, Treatment and Prevention
Abstract no. CDB144

Suggested Citation
"MazzaF., et al. HIV protease inhibitors and mammalian proteasomes: what's that got to do with pneumocystis?. : 4th IAS Conference on HIV Pathogenesis, Treatment and Prevention: Abstract no. CDB144"

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