We have discovered human platelet microbicidal proteins (PMPs) that are microbicidal chemokines, termed human platelet kinocidins (hPKs) to reflect their microbicidal and chemokine functions. hPKs have previously unrecognized microbicidal activity in human blood, but differ markedly in structure from cytotoxic defensin-like peptides. Thus, hPKs have unique structure-activity correlates to confer microbicidal activity without concomitant cytotoxicity. Specific hPK domains confer direct antimicrobial activity, and have amplified microbicidal activity in environments simulating acidic phagolysosomes. Distinct hPK domains promote neutrophil phagocytosis and intracellular killing of pathogens. We hypothesize that specific determinants in hPKs govern these independent but complementary antimicrobial functions. Yet, structural determinants responsible for the coordinated host defense roles of hPKs are unknown. We propose these determinants can be identified, their antimicrobial features defined, and structure-activity signatures resolved. Our complementary Specific Aims will explore these hypotheses:
Specific Aim 1 : Identify the structural determinants governing direct microbicidal functions of hPKs. We will assess peptide libraries of key hPKs to identify domains that confer relevant microbicidal functions. Strategic mutant peptides and synthetic analogues will be used to isolate precise structural determinants responsible for the shared or unique microbicidal profiles of distinct hPKs.
Specific Aim 2 : Define the roles of specific hPK domains on key neutrophil antimicrobial functions. We will dissect hPK domains that potentiate neutrophil phagocytosis, oxidative burst, or intracellular killing in vitro using multicolor flow cytometry. These studies will define which hPK domains enhance the key antimicrobial mechanisms in neutrophils directly, or by augmenting the inherent capabilities of these cells.
Specific Aim 3 : Resolve structure-activity relationships (SARs) in hPK antimicrobial determinants. We will resolve SAR themes in hPK determinants using complementary NMR, CD, and FTIR studies to guide molecular modeling. Unique to our studies will be mosaic peptides designed to validate and interchange the roles of functional signatures in distinct hPKs. These approaches will identify the specific SARs and functional determinants that may be specific to or shared among distinct hPKs or other kinocidins. Our discoveries create a unique opportunity to define molecular signatures in hPKs that govern their multiple antimicrobial functions in innate and adaptive immunity. In turn, these insights will accelerate development of novel strategies to prevent or treat serious infections, particularly those caused by antibiotic-resistant pathogens. ? ?

National Institute of Health (NIH)
National Institute of Allergy and Infectious Diseases (NIAID)
Research Project (R01)
Project #
Application #
Study Section
Special Emphasis Panel (ZRG1-DDR (01))
Program Officer
Peters, Kent
Project Start
Project End
Budget Start
Budget End
Support Year
Fiscal Year
Total Cost
Indirect Cost
La Biomed Research Institute/ Harbor UCLA Medical Center
United States
Zip Code
Sakoulas, George; Okumura, Cheryl Y; Thienphrapa, Wdee et al. (2014) Nafcillin enhances innate immune-mediated killing of methicillin-resistant Staphylococcus aureus. J Mol Med (Berl) 92:139-49
Yeaman, Michael R (2014) Platelets: at the nexus of antimicrobial defence. Nat Rev Microbiol 12:426-37
Jung, Sook-In; Finkel, Jonathan S; Solis, Norma V et al. (2013) Bcr1 functions downstream of Ssd1 to mediate antimicrobial peptide resistance in Candida albicans. Eukaryot Cell 12:411-9
Yang, Soo-Jin; Xiong, Yan Q; Yeaman, Michael R et al. (2013) Role of the LytSR two-component regulatory system in adaptation to cationic antimicrobial peptides in Staphylococcus aureus. Antimicrob Agents Chemother 57:3875-82
Mishra, Nagendra N; Yang, Soo-Jin; Chen, Liang et al. (2013) Emergence of daptomycin resistance in daptomycin-naïve rabbits with methicillin-resistant Staphylococcus aureus prosthetic joint infection is associated with resistance to host defense cationic peptides and mprF polymorphisms. PLoS One 8:e71151
Gao, Wei; Cameron, David R; Davies, John K et al. (2013) The RpoB H???Y rifampicin resistance mutation and an active stringent response reduce virulence and increase resistance to innate immune responses in Staphylococcus aureus. J Infect Dis 207:929-39
Yount, Nannette Y; Yeaman, Michael R (2013) Peptide antimicrobials: cell wall as a bacterial target. Ann N Y Acad Sci 1277:127-38
Yount, Nannette Y; Yeaman, Michael R (2012) Emerging themes and therapeutic prospects for anti-infective peptides. Annu Rev Pharmacol Toxicol 52:337-60
Erfe, Marie Crisel B; David, Consuelo V; Huang, Cher et al. (2012) Efficacy of synthetic peptides RP-1 and AA-RP-1 against Leishmania species in vitro and in vivo. Antimicrob Agents Chemother 56:658-65
Yang, Soo-Jin; Bayer, Arnold S; Mishra, Nagendra N et al. (2012) The Staphylococcus aureus two-component regulatory system, GraRS, senses and confers resistance to selected cationic antimicrobial peptides. Infect Immun 80:74-81

Showing the most recent 10 out of 26 publications