Sepsis-Induced Cardiac Mitochondrial Dysfunction Involves Altered Mitochondrial-Localization of Tyrosine Kinase Src and Tyrosine Phosphatase SHP2

Abstract

Our previous research demonstrated that sepsis produces mitochondrial dysfunction with increased mitochondrial oxidative stress in the heart. The present study investigated the role of mitochondria-localized signaling molecules, tyrosine kinase Src and tyrosine phosphatase SHP2, in sepsis-induced cardiac mitochondrial dysfunction using a rat pneumonia-related sepsis model. SD rats were given an intratracheal injection of Streptococcus pneumoniae, 4×106 CFU per rat, (or vehicle for shams); heart tissues were then harvested and subcellular fractions were prepared. By Western blot, we detected a gradual and significant decrease in Src and an increase in SHP2 in cardiac mitochondria within 24 hours post-inoculation. Furthermore, at 24 hours post-inoculation, sepsis caused a near 70% reduction in tyrosine phosphorylation of all cardiac mitochondrial proteins. Decreased tyrosine phosphorylation of certain mitochondrial structural proteins (porin, cyclophilin D and cytochrome C) and functional proteins (complex II subunit 30kD and complex I subunit NDUFB8) were evident in the hearts of septic rats. In vitro, pre-treatment of mitochondrial fractions with recombinant active Src kinase elevated OXPHOS complex I and II-III activity, whereas the effect of SHP2 phosphatase was opposite. Neither Src nor SHP2 affected complex IV and V activity under the same conditions. By immunoprecipitation, we showed that Src and SHP2 consistently interacted with complex I and III in the heart, suggesting that complex I and III contain putative substrates of Src and SHP2. In addition, in vitro treatment of mitochondrial fractions with active Src suppressed sepsis-associated mtROS production and protected aconitase activity, an indirect marker of mitochondrial oxidative stress. On the contrary, active SHP2 phosphatase overproduced mtROS and deactivated aconitase under the same in vitro conditions. In conclusion, our data suggest that changes in mitochondria-localized signaling molecules Src and SHP2 constitute a potential signaling pathway to affect mitochondrial dysfunction in the heart during sepsis.

Sepsis-induced brain mitochondrial dysfunction is associated with altered mitochondrial Src and PTP1B levels

“…We observed that the activities of complex I-V were substantially decreased in SIBD, and that active Src and PTP1B could regulate complexes I, II, and III activities in vitro. These results are similar to previous studies by Zang et al (2012). Interestingly, work from the laboratories of Arachiche et al (2008) andHebert Chatelain et al (2011) have demonstrated that the Src inhibitors PP1/PP2 and PTP1Bi can affect complex IV/V activities in the rat brain.…”

Soluble Heparan Sulfate in Serum of Septic Shock Patients Induces Mitochondrial Dysfunction in Murine Cardiomyocytes

“…Impaired mitochondrial function in sepsis involves a variety of pathological mechanisms, such as compromised energy generation and elevated production of mitochondrial reactive oxygen species (mtROS) (9,10). Members of the nuclear receptor transcription factor superfamily, including peroxisome proliferator-activated receptors (PPARs), control the expression of many genes involved in mitochondrial regulation.…”

Journey to the Center of the Mitochondria Guided by the Tail Anchor of Protein Tyrosine Phosphatase 1B

“…As mentioned above, previous studies have revealed a significant mitochondrial population of the non-receptor tyrosine kinase c-Src as well as other members of the Src family 33,[36][37][38][39][40] . To probe Src family activity at the mitochondria, we examined the localization of the dSH2-YFP probe in COS-7 cells.…”

“…regulation of mitochondrial EGFR signaling [41][42][43] ) and in the mitochondrial interior (e.g. regulation of activities of Src 33,36-40 and SHP2 33,40,44 , regulation of electron transport chain enzymes 34,35 ). Further investigations of PTP1B's interactions with known and putative substrates using standard biochemical approaches or advanced microscopy would be useful.…”

“…PTP1B's potential presence at the mitochondria could be important for regulation of the mitochondrial phosphotyrosine proteome 34 , with important targets including several enzymes in the electron transport chain 35 , Src family kinases that localize to the mitochondria 33,[36][37][38][39][40] , or other well-established substrates of PTP1B that also have been detected at the mitochondria like the EGF receptors ErbB1 41,42 and ErbB2 43 and the tyrosine phosphatase SHP2 33,40,44 . PTP1B's mitochondrial localization, though, should be confirmed first (in particular, for more general cell lines), before further speculating on how it may reach this organelle or how its interaction there with putative as well as known substrates might affect basic mitochondrial functions.…”